I've been using the Firefox mod Zen Browser on Linux Mint. When Firefox released an update in February, my Zen had it the next day. People depending on the "official" Firefox were left waiting over a week, with multiple threads in the forums asking "when is it coming?"

Also when I looked into mods updates for a critical security fix in November, practically all the mods had updated within 24 hours of FF's update. (Exceptions: Midori and Mercury.) https://forums.linuxmint.com/viewtopic.php?p=2554267&sid=4f140800c5d62939af8e6394514b9aab#p2554267

"Zen is no good if you care about privacy."

How so?

Used Webkit until 2019, then bought out and now based on Firefox/Gecko.

There are tools to update AppImages, like AM and Gear Lever.

Well, you can get Bottles as an AppImage... unofficially https://github.com/ivan-hc/Bottles-appimage