This post has some slight overlap with my other post here as it does involve the left sidebar element: Phone Sidebar Usability
On the smartphone (Android, Pixel 6 Pro), My experience with the bottom ribbon menu button is…okay, but it has far more friction for me to use than the side-ribbon as found on desktop/tablet.
I also happened to notice that the sidebars as it stands do not use up the entire screen (there is a full screen button, but I never use it).
Why not migrate the ribbon menu over to the left of the left sidebar when opened? This would also bring the design language in line with that of the tablet or desktop, albeit in a condensed form.
In addition, it would then make the sidebar properly use the entire screen.
If there were too many ribbon buttons, it could be scrolled through, or given an overloading button to show the rest.