Making and submitting an App built with Flutter and SqLite

Hi, I have an app that I released in win, macos, ios, android, and appimage.
Our app is released in all official channels except appimage hub.

I’d like to release a flatpak, but I’m quite intimidated to do this.

Is there someone who is an expert on this who can hold my hand for making a build.
The build is complex. It has a db that needs to be downloaded separately. Then one needs to extract the 7z file and then call a bash file. It also needs sqlite3 in order to work.

I have an AppImage because the snap experience totally failed.

The name of the project on github is called tipitaka pali reader
under my repo bksubhuti.

Please take a look and send a message here or private.
Our App is noncommercial oss.
Android alone has 1800 installs.
MS App store has about 200
Apple has about 300