(This is probably related to the change with the new admins group in Yunohost 11.1 … you should try to log using a member of the admins group instead of admin@)
If it is the same problem (and it may not be as I force upgraded my_webapp 's to get the config screen working so it may be something else) I have it on all my web apps using filezilla either with an admin or my_webapp username. Previously all these worked.
Weirdly though, sftp still works in publii and over the command line.
sftp -P 666 my_webapp@blahblahblah works fine.
So this may be a Filezilla specific problem.
And, having installed 3.62.2 from Flathub it appears it is a Filezilla problem, or at least my one is. All my web_apps that don’t work under the old version of Filezilla 3.52.2 are working under 3.62.2.
If you are going to try this, don’t forget to backup your old Filezilla config folder (under ~/.config on Debian) as writing to it with the updated version will cause problems if you move back to the old. You can also export your config from Filezilla File/Export which is a good idea as well.
Just noticed that the Filezilla flatpak doesn’t recognise the default text editor, at least on my computer (deb 11, kde). If you have this problem, then dump the flatpak and do this.