Latest 3.1.1 and 3.1.2 Linux desktop clients do not work

I run Ubuntu 20.04 LTS and none of the recent desktop sync clients seem to work for me. I can authenticate but then files never actually sync. This applies to the Debian PPA based nautilus-nextcloud as well as the AppImages v3.1.1 and v3.1.2. Is anyone else experiencing this problem?

I kept trying older releases until I got to one that works for me: v3.0.1.

I have a similar problem when using the appimage v3.1.3 - but for me, it selectively syncs some files, but not others (without error message of any kind).
The missing files are not synced downward form the server, and they all have Chinese filenames.
So, with appimage 3.1.3, syncing of files with Chinese characters in their name doesn’t work for me.
I went back to my distribution package (Ubuntu 20.10, 2.6.4) and now the Chinese filenames are being synced again.

Any advice?