I saw a recent post regarding someone that's interested in joining/making a flutter dev group in order to learn and share more about flutter, personally I think its a great idea, it's somewhat hard to find people or a small group of people that are interesting in collaborative flutter projects (as a good hobby, otherwise I would understand if you charge money for your work) since -in my own personal experience- the community is not as ample as other programming languages, and finding help for outdated dependencies or anything of that sort is extremely hard to find.
There is a lot more to making Apps than coding!
I am learning about UX / UI Design -VERY important, your app can be coded perfectly but if the user feels it's hard to find things as well as colors are off and appeal isn't there then your App will struggle a bit-, color pallets, design systems, iOS and Android ecosystems, as well as making my own UX/ UI case studies that I plan to publish once they are polished up.

This being said if there is anyone that has an interest in working with a fitness / gym app as well as a check-in system made in flutter firebase drop a comment or DM me, I can teach you the little I know and vice-versa. I have been working on a fitness app for about a year and a half and it's been going pretty well, I've made a lot of progress and it's thanks to this community I was able to publish it in the App Store and Play Store. The App is essentially "done" and is functional, but if someone has a genuine interest and would like to collaborate and share ideas then by all means I'd appreciate your support.