Duplicati won't start: "This is likely caused by upgrading to a newer version and then downgrading"

Not reported very loudly, only by

The code used to be in UpdateManager in a catch inside RunMethod.
Stack traces above show it at work. That plan got removed for NET 8.

I just now tested with a manually too-high Version to check the result.

Two Application event log entries similar to 2.0.8.1 above were made.
Terminal output was made without having to suppress an autoupdate.
Duplicati-crashlog.txt was not made, at least that Everything shows.

Duplicati.GUI.TrayIcon.exe.5668.dmp was made.
in AppData\Local\CrashDump. I don’t know if 2.0.8.1 does this as well.

Yes. The seeming downgrade to 2.0.8.1 after the upgrade.to 2.0.9.111.

is unclear. @dhzl84 did you manually reinstall 2.0.8.1 again before hitting the “won’t start”?

EDIT:

Maybe 2.0.8.1 install was on list above as “5 Install release”. If so, that explains its presence and removes my concern that the new release found a way to downgrade unexpectedly like old may. Manual downgrade to avoid a new FTP issue is more appealing from an upgrade-bug viewpoint.