After struggling forever, I finally got yt-dlp to work.
First set USER_ID = 99, GROUP_ID = 100, UMASK = 000 in template.
Then, download yt-dlp_linux from https://github.com/yt-dlp/yt-dlp?tab=readme-ov-file#release-files and rename it yt-dlp. Upload to the addons folder in your TMM appdata folder.
Finally, make sure TMM is stopped, open the console, and run the following commands (change the TMM directory to match yours):
sudo chown -R nobody:users /mnt/user/appdata/TinyMediaManager
sudo chmod -R u=rwx,g=rwx,o=rx /mnt/user/appdata/TinyMediaManager
Start TMM and it should be happy to download trailers from YouTube.