I dove into Appcelerator Titanium as a novice developer with very little experience in Javascript. I put an app in the Apple App Store within a few months by working nights and weekends. If you (1) want to write code, (2) want a native app, and (3) don't have prior experience with Objective C or Java, OR (4) want to write less code and deploy faster, then I recommend Titanium. If you (a) don't want to touch the code, (b) have some compelling feature that requires lower-level access than what is offered by Titanium (I don't know what this might be), or (c) have significantly more experience with a relevant programming language and don't want to learn Javascript, then there are surely more appropriate alternatives.

Definitely go with PhoneGap.
Learning curve for web technologies (HTML, css & javascript) is the most compelling out there.
These have been around for decades and you can find all sorts of tutorials, sample code, discussion, and frameworks.

Phonegap is sweet - however, I think the bigger question is - how involved with the framework do you want to be? How senior will your development team be? Maybe this team is an army of one? You?

While you are open to ideas, why not look at some of the game engines that use a development platform with data integration capabilities?

Cheers -

What framework you use depends on your experience and knowledge of the corresponding programming language. I would also recommend looking into Xamarin, which allows you to create native applications for all platforms while writing code in C#

I would be happy to discuss further if you would like to jump on a call.

Ionic Framework would be my No.1 choice!
Appgyver just came out with upgrade, you should check it out!

But Ionic Framework rocks!

I usually recommend either React Native or Flutter. Both produce professional looking apps that support both iOS and Android. React Native's advantage is that it is based on React, so you can combine some work if you want to have both a web and mobile interface. Flutter's got a nice, quick development style. Either one will give you great results though.

Since you have already checked phonegap, bootstrap, appgyver and ionic, I will deal with the other frameworks that may be a great help to you. I will go with Xamarin or React Native as second best options, but the others are good as well.
1. Xamrin: Xamrin is an intelligent way to build an app, developers can use C# for Android, iOS, and Universal for Windows apps. It is one of the reliable tools that provide flexible native performance. Backed with Microsoft technology, it has approx. 1.4 million developers of the community. With an excellent native user interface, it not only helps developers to build a native app with ease but also controls the app to give ultimate user experience.
Advantages of using Xamarin Framework for your Mobile Projects
Benefits of Xamarin:
1. Native User-Interface
2. Xamarin has great native user interface & controls which allow you to create a native app.
3. Cross-Platform App Development
4. Xamarin is now included to Visual Studio with no extra cost including Visual Studio Community version which is free for Individuals, open source projects and smaller teams. So, Low-Cost development. Get a cost estimation of Xamarin mobile app development
5. Xamarin is a perfect choice for Cross-platform app development.
6. Allows you to build Apps for Windows, Android, and iOS app & also share codes over multiple platforms.
7. Easier API Integration
8. Useful compiled code
9. Xamarin mobile App Framework allows you to generate productive and high-performing code that can access every native API
10. Huge community and Support are available on official forum and third parties’ websites.
11. Shared Code Base

2. React Native: From Startups to Fortune 500 organizations, React Native is one of the popular frameworks in 2019–20 which is used to build both Android and iOS apps. React Native development allows mobile app developers to build high-performance apps in shorter development cycles and faster deployment times. React native deals with JSX thus there is no need for developers to learn more complex programming languages for developing Android or iOS apps. Moreover, it provides extremely smooth animations as the code is converted into native views before rendering.
Benefits of React Native:
1. Reusability: React Native was originally developed by Facebook to design the user interface of its mobile application. In the beginning, the React Native framework only worked with iOS.
2. Efficiency: The benefits of React, such as high performance and a virtual DOM, carry over to React Native as well. Using React Native can make you more efficient and speed up your development times in a variety of ways.
3. JavaScript: JavaScript has risen from its lowly origins to become the king of web programming languages. Nearly everyone calling themselves a “web developer” has had a good deal of experience with JavaScript.

3. Corona SDK: Instead of large development teams, Corona SDK helps developers in building solitary code base that functions amazingly-well with Android, iOS, and Nook. Utilizing its features, Corona SDK includes interactivity and delightful graphics content into the apps. Also, Corona SDK app development scales content automatically across multiple devices. Gaming APIs are easily included to your app and allow you monetize app easily and quickly.
4. jQuery Mobile: jQuery is a ready-to-use JavaScript library having various plugins like Image Slider, Content Slider, and Pop-Up Boxes, etc. The jQuery is easier than JavaScript libraries, as less code is written to attain the same features in comparison to other libraries. It makes web pages simpler, interactive, and user-friendly. It is completely readable by all search engines and is optimized in terms of SEO.
5. Intel XDK: With a single code base, Intel XDK lets developers build mobile apps for iOS, Windows, Android, Amazon, and Nook. The main reason why developers use Intel XDK is that it comes with a drag-and-drop user interface thus interfaces are easily built. It comes with profiling and app debug options thus testing the app on different device configurations made easy.
6. Flutter: Flutter is a software development kit from the house of Google that attracts developers by leveraging them for faster coding. It makes the app development process more convenient by providing a single code base for Android and iOS. Flutter gives an advantage of modifying the old widgets and creating a new one effortlessly. Thus, helps to build responsive mobile applications that engage your target audience within a short period.
7. Mobile Angular UI: Mobile Angular UI consists of many interactive components like switches, overlays, and sidebars thus deliver a robust mobile experience to its users. There are a lot of benefits of this structural framework which makes it a smart choice for modern-day web applications. It is an open-source framework that helps in developing rich internet applications. Being a cross-browser compliant, Mobile Angular UI automatically handles JavaScript code suitable for each browser.
8. Appcelerator Titanium: If you are looking for a one-stop mobile application framework, Appcelerator Titanium is the right choice. It features independent APIs that make accessing mobile device hardware relatively smooth and reliable. Appcelerator Titanium uses native UI components thus delivers good performance to its user base. After considering various factors like development time period, budget, operating systems, and much more, we have provided the list of Mobile App Frameworks For 2019–20. You can also consult a reliable mobile app development agency to choose the right framework for your app project.
9. Swiftic: One of the most easy-to-use mobile app development frameworks, Swiftic is available for the iOS platform. Besides an easily navigable interface, it is a convenient option with assorted features like push notifications, in-app coupons, scratch cards, app promotion, social media feeds, and much more. There are more than 1,000,000 apps that are created with this framework and are currently running on the marketplace. Whether you are running an e-commerce business or restaurant, the framework allows developers to build custom applications based on outlaid business requirements.
10. Sencha Touch: A high-performance HTML5 mobile application framework, Sencha Touch is used to build applications that enable world-class user experiences, intuitive touch, and dynamic interfaces. It is the first choice for developers when it is time to build enterprise application development. It is packed with various widgets that are ready-to-use that are popular for all platforms like iOS, Android, and Windows. Being one of the mobile app development frameworks, Sencha Touch uses the hardware acceleration to improve the performance of already-built applications. Moreover, it provides high-grade security while developing robust applications.
11. Native Script: Many top mobile app development companies love to use Native Script. Built with JavaScript; Native Script is used to develop top-notch cross-platform apps for both Android and iOS. It can use the full features of a device like a camera, GPS, and contacts and develop high-level enterprise apps. Apps built with Native Scripts can help you save enormous money in the long run. The mobile app developers can reuse the code and tools in other apps too. Native Script and Ionic are two famous frontend frameworks where Ionic focuses on building high-performance apps using the latest web technologies while Native Script focuses on building Native UIS using a single codebase.
Besides if you do have any questions give me a call: https://clarity.fm/joy-brotonath