Hover a thumbnail on youtube.com and click an icon at the right: "Not interested" and "Don't recommend channel"
< Feedback on YT: not interested in one click
1.3.3 should handle shorts. As for the second issue, I couldn't reproduce it, so I guess youtube site is slightly different for you as they regularly experiment with random users...
Shorts in main page fixed indeed, but the sidebar ones still lacked.
Force an update, it was fixed in 1.3.4.
Pressing "no interest" button did nothing and caused another new issue.
This bug only happened on main page while the scrolling of recommended videos. It would result in that nearby videos miss ┆ buttons and must reload current page to solve this issue.