I got onto the phone with Samsung technical support, and this is what they had me do
Do the usual delete all data, uninstall, reinstall. This didn’t fix it.
After re-install, I signed into Microsoft in the usual way, and the problem was still there.
I then signed out of Microsoft, but I didn’t sign in in the usual way. I signed in manually, giving new e-mail etc., rather than letting it do things automatically. This is what seemed to fix it.
I hope this helps someone else. I did do it in conjunction with Samsung remote access, and things happened a bit quickly (they did the signing out and told me what to do), so I hope I have got the details right.
So the problem seems to be connected with the Microsoft sign-in.
Is it possible to downgrade to a version that works?
A bit more info: I have, what appears to be 2 Microsoft accounts, one with my real e-mail address and one with my gmail address, which I don’t use but have to have by virtue of having an Android tablet. When it is auto-signing in it seems to randomly pick my gmail address instead my my normal e-mail address, but my realms login, etc. is with my normal e-mail address. However, I can’t find a means of getting rid of the gmail-based Microsoft login (or not yet, at least)