Firefox 91.7.1 / iMac
GREAT extension, I have a ton of subscriptions and this add-on allows me to quickly see new uploads organized into groups of my own creation...without have to scroll through dozens of channels individually. Bonus: the channel display of groups in YouTube Subscription manager defaults to their "uploads/video" list. Otherwise I often have to click that link on a subscribed to channel to bypass their intro videos/shorts/playlists or w/e. Good stuff!
The only "glitch" that doesn't even bother me is often having to re-load the Youtube main page to get YTSM to display new video counts next to my groups...like it needs to read the home page after it loads up or something...otherwise it's 100 percent.