Notifications not working on /e/OS (with MicroG)

[ne20002]

⚠️ Before posting ⚠️

• [X] This is a bug, not a question or an enhancement.
• [X] I've searched for similar issues and didn't find a duplicate.
• [X] I've written a clear and descriptive title for this issue, not just "Bug" or "Crash".
• [X] I agree to follow Nextcloud's Code of Conduct.

Steps to reproduce

Use a phone with /e/OS (or MicroG)

While other Apps like e.g. WhatsApp, Signal, SBB, ZVV, MeteoSwiss do work with Firebase Cload Messaging the Nextcloud app does not. Indeed, on the notifications tab in the app a message box appears claiming that Google services are not available.

Expected behaviour

Nextcloud Android app should work with MicroG and not depend on Google services directly but use the correct API.

Actual behaviour

Notifications not working

Android version

10 /e/OS

Device brand and model

Samsung S9

Stock or custom OS?

Custom (explain in "additional information")

Nextcloud android app version

3.21.2

Nextcloud server version

24.0.5

Using a reverse proxy?

Yes

Android logs

N/A

Server error logs

N/A

Additional information

Please see also #https://github.com/nextcloud/android/issues/8684