As you can see in the video above (I uploaded it again - not sure why it was broken today) I had enabled safe mode.
The current version is 2a08d5d (It was different when I wrote the report). I can also repro here - I only chose my forum because admins have more options so the hidden menu was better visible. On Meta it’s barely visible. Most of the time it seems the button wouldn’t work at all
I am using a Samsung Galaxy Tab S9 FE (Android 16) with Firefox
I have just checked Chrome - it seems to be the same:
Usually this kind of issues are because my tablet has “desktop-size” but is touch. Similar to the problems here or here