Zen: On one machine, Flatpak. On the other, AppImage through AM.
Firefox: Mint-maintained version from Mint repo (deb).
I can’t remember the exact differences between Firefox upstream and Mint version. But I believe Mint began maintaining their own deb at a time when upstream Ubuntu was only offering Firefox as a snap, which Mint is against, and Mozilla hadn’t yet begun offering their own deb repo.
Zen: On one machine, Flatpak. On the other, AppImage through AM. Firefox: Mint-maintained version from Mint repo (deb).
I can’t remember the exact differences between Firefox upstream and Mint version. But I believe Mint began maintaining their own deb at a time when upstream Ubuntu was only offering Firefox as a snap, which Mint is against, and Mozilla hadn’t yet begun offering their own deb repo.
That’s where the delay comes. Though I guess it does point out that even with just Firefox the differences are small in how quickly you get updates.