Interesting, funny enough I have sorta the opposite problem using Firefox for PDFs: I like the side by side view of two pages and Firefox always loads books with single pages, zoomed way too far in for my taste. Have you tried it for PDFs recently? It’s a new way of reading them for me, and I wonder if they’ve changed it since you used it last.

I actually really like Firefox for reading pdf’s, how is it in chrome? I’ve never actually tried chrome for that because I was still using okular back when I still had chrome installed on anything.

This isn’t a direct replacement for tab groups, but there’s a Firefox extension called Tree Style Tab that organizes your tabs into a nested tree structure. I use it a lot to emulate tab groups and the way it lays out the tabs makes it much easier to read imo. It might be worth taking a look if tab groups are chromium’s “killer feature” for you.

If you don’t mind me asking, are there any other must-have features that chromium has that Firefox doesn’t?