Registration Screen (optional) or similar forms in SAB apps

Currently Registration screen is shown when a user launches the app for the first time.

Can this also be made as an optional feature?

Eg. Scnearios

Signup Form in Sidebar Menu
If user is interested to know more or connect with a local church, he can sign up using the form provided in sidebar.

Sign in to Bible App
This can be also used to create an account with the app (user data stored in Google Firebase Database, and users could store their bookmarks, notes etc. and sync back data when they sign in with a new device (or retrieve their notes if they lost the device/reinstalled the app).
See related request here.

More ideas for Forms in SAB? Thoughts are welcome.