I see in your log that the update didn't work:
It should say: Compiled: 2020-09-29Code:Looking for SiteUtils and Hosters in OnlineVideos.Sites.offbyone.dll [Version: 2.3.1.0 (git master 075f0bb859bf5914dc1a1f755f7058f83ebbb591), Compiled: 2020-09-25 13:21:31]
if after the update it still doesn't work:
Can you close mediaportal, open mediaportal.xml (in C:\ProgramData\Team MediaPortal\MediaPortal) and remove the line
Then start mediaportal, go to onlinevideos\youtubeCode:<entry name="YouTubeV3apiStore.user">lotsoftext</entry>
Then you should see your browser starting asking to choose an account, then a warning about the app not being verified.
Click "advanced", "Go to Onlinevideos (unsafe)", "Allow" twice.
From then on, youtube should work as expected.
I couldn't get it to update and couldn't find that line i mediaportal.xml but i did go to onlinevideos settings and changed login to false started mediaportal and went to youtube, went back to onlinevideos settings and changed login back to true, started mediaportal and went to youtube and was asked for a login.
It's working fine now.