[com.twoscape.sportler] Google login not working

Affected app
Name: [Sportler Ski Tracker]
Package id: [com.twoscape.sportler]

Describe the bug
Sportler is a ski tracking app with location sharing / leaderboards using Google Sign-In. Trying to log in with microg installed does not work (just showing "failed" and generating logcat below)

To Reproduce
Steps to reproduce the behavior:

1. Open "Sportler"
2. (Scroll down to "friends" on the startpage, if needed)
3. Select "friends"-switch to on (default: off), prompting google-login
4. Select "Sign in with google" in the dialog
5. Select google account in microg dialog
6. See error

Expected behavior
Google login should succeed, turning the switch next to "friends" to on. If friends have previously been found or tracks have been recorded, they should be synced now. Furthermore, the settings activity should show account logged in status, giving the option to log out.

Screenshots
Logcat: (if some other lines are important, I can provide them, too)

In the following, location info and google account have been blurred.
App start page, not logged in:

Google Sign-In dialog:

Microg google sign-in dialog:

Error shown on startpage after login:

System
Android Version: [13]
Custom ROM: [LineageOS with microg 20.0]

microG
microG Core version: [0.3.0.233515]
microG Self-Check results: [All ticked]

Additional context
Willing to help fixing this issue, but unsure how. Can provide more info / logcat output, if needed

Start by reproducing the Sportler Google Sign-In flow on Android 13 with microG Core 0.3.0.233515 and inspect the supplied logcat around account selection and the resulting failure. Done means the friends switch can enable successfully, account status appears in settings, and previously recorded tracks or friends sync as described.