My Ultra 4800X just updated to the latest Version/Build, 10.0.0 Build 4205-C2 and, since then, numerous apps, are not functioning properly. Fubo and Hulu are unable to load channels or the channel guide and the Tablo Tablo app cannot connect to Tablo (even though my iOS app can).
The Roku Dev team needs to rollback Build 4205-C2 ASAP
All the apps are behaving normally on my 4800 and build 4205, including Hulu (I dont have Hulu Live TV, which you imply you have), though I cant test FuboTV or Tablo (dont subscribe/use).
FYI, there was a Hulu app update (6.43.2) yesterday as well, which may be the source of the Hulu problem (could have been Fubo and Tablo updates too for that matter).
If you haven't already:
1) Check for updates again (Settings/System/System update/Check now) - try again
2) Restart your Roku (Settings/System/System update/Check now) - try again
You may or may not be able to revert your firmware: Official ROKU 4K (HDR) Premiere +/Ultra Owners Thread | Page 788 | AVS Forum
I have found that a Roku version update doesn't always bring with it an update of all installed channels. After each Roku update I always manually start an additional update as @StreamerUser suggested, and it often updates a handful of channels to versions keyed to the new Roku version.