I use GrapheneOS, and there is an App Store called Accrescent which can be installed and used on any android devices.
If you can, make your app available there too as updates are available there faster compared to fdroid.
There are over 150k GrapheneOS users around the world and right now there are very few apps available in Accrescent app store like organic maps, Molly, IVPN, cryptomator etc., although many apps are slowly getting added.

The process is simple, contact the Accrescent team over email with your project, and ask them "to whitelist your project" so that you can make your apps available there.

And also, if you guys do this, you will be the first privacy email provider whose app will be available there.