Update check not working 2.0.5.114_canary_2021-3-10

Yes. It checks for updates for whatever channel you’re in. 2.0.5.114 is the latest Canary.
You can find your channel in About → System info, e.g. DefaultUpdateChannel : Canary
You can find it and control it in Settings. A fresh install changes channel type to its type.

Are you sure? 2.0.5.114_canary_2021-03-10 is extremely close to 2.0.5.113, per that link.
I don’t think this can be tried on previous versions now because now there are new ones.

“Check for updates now” status indicator also mentioned this before in forum UX category.

I’d note that CLI tool does better:

C:\ProgramData\Duplicati\duplicati-2.0.5.114_canary_2021-03-10>Duplicati.Library.AutoUpdater.exe check
No updates found

C:\ProgramData\Duplicati\duplicati-2.0.5.114_canary_2021-03-10>Duplicati.Library.AutoUpdater.exe install
You are running the latest version: 2.0.5.114_canary_2021-03-10 (2.0.5.114)

C:\ProgramData\Duplicati\duplicati-2.0.5.114_canary_2021-03-10>