I had been having trouble with slow starts of firefox-esr in Debian Bullseye, but it seems to be resolved with the latest update https://tracker.debian.org/pkg/firefox-esr
I've been back in Debian 11 for a month and a half, and things have been smooth — as expected. Pretty much everything has been running well, and overall the laptop is staying very cool.
My favourite computer, an old Mac - Connor Oliver/Muezza.ca http://muezza.ca/thoughts/favourite_computer/