uBlock Origin and Sponsorblock works on Firefox for Youtube even signed in

Yes, there is no question about that the uBlock Origin works regardless of your YouTube session status. The question is whether YouTube's countermeasures kick in or not: nagging you to turn it off, or stop playback.

Your comment is so useful that I actually created an account just to thank you for your wisdom.

Im logged in and see no ads. Safari with adguard, no ads on mac or phone. Update: i do see ads on safari mobile now.

The issue isn't whether you see ads or not, but whether YouTube is nagging you to turn off your ad blocking on threat of video playback being suspended after a few videos.