2FA and OTP failure

I am running Nextcloud 15.0.7 on Debian. It tells me there is an update to the Two Factor TOTP Provider app, but when I try to update it, I get a pop-up error that says

An error occured during the request. Unable to proceed.
Couldn’t update app.

I’m not grumbling about getting an error message. I am grumbling about the uselessness of the error message. What sort of error occurred?
It should say what it know, or it should say it doesn’t know what the error was. It should give some clue to how to resolve the problem.
Being unscrutable is not a message!

Can anyone suggest what might be wrong?

Related to that, I’d quite like to try using 2FA, but preferably not using the Google app. There are two other Android apps suggested.

One has disappeared from the Play Store (and I can’t find it anywhere else, even if I was prepared to install a security app from some where else)
The other hasn’t been updated since 2016 and appears to be abandonware. Reviews suggest that it isn’t good for recent versions of Android.

Is there a good app to install on Android?

You should open the log viewer (*Settings>Administration>Logging) and check the messages or directly access the Nextcloud log file for more detailed information about the root cause of the problem. If you don’t line the Google Authenticatior, you can e.g. use AndOTP.