>>105703031
Ok I installed Ubuntu and did some testings, and indeed it is more compact.
Firefox had a dedicated space for extension icons at the left + the text space. Now the icon and text occupy the same space.

The change was already present on Windows, now they modified it on Linux.

I'll check if there's a way to revert back, but it should be fine. Picrel is the comparison on Firefox 139 and Firefox 140 on Ubuntu 22.