Can't close tabs on macOS Big Sur
New install of macOS Big Sur and latest Firefox for Mac. There is a bug that is preventing tabs after the second tab from being able to close. It doesn't seem to matter if those tabs are in focus or not.
Try to update to Big Sur beta 7 if you haven't done this yet, as that might have a fix for this issue.
Note that there might still be a very small active area at to bottom of the tab bar.