Years ago, a #Firefox fork called #Flock had a social tool built in. I only used it for #Twitter, but it was there. Memory is unclear whether it was a side panel or another Window with different measurements, but it existed.
Also, #Vivaldi now has its own #Mastodon instance. I think #Brave Browser had an unofficial instance at one time, and #Mozilla intends to open theirs early in 2023.
I'm still not "there" yet, but I am doing some #PHP stuff. Maybe I'll be able to help make !GNUsocial and #Friendica competitive candidates for $ORGANIZATION deploying their own #Fediverse presence.