It uses the existing FF container functionality, so uBlock should not be affected. I also use uBlock and haven't noticed anything bizarre. Maybe you just used YouTube right before a necessary update to uBlock's filters got loaded.
Regarding login, it's a struggle with any container addon. But I like how this one makes it easier. It streamlines it a bit because you can right click the page and go to Auto Containers -> Exclude tab from domain exclusions, then login as normal and add each intermediate domain to the container's URL patterns. It would be nice if the dev could add a way to record all intermediate domains and add them at the end; sometimes I miss one or two due to an auto-redirect.
Regarding login, it's a struggle with any container addon. But I like how this one makes it easier. It streamlines it a bit because you can right click the page and go to Auto Containers -> Exclude tab from domain exclusions, then login as normal and add each intermediate domain to the container's URL patterns. It would be nice if the dev could add a way to record all intermediate domains and add them at the end; sometimes I miss one or two due to an auto-redirect.