After creating a fresh installation of Ubuntu 24.04, I installed DEB Firefox from APT by following Mozilla’s instructions from here. But I noticed that it was secretly replaced with Snap Firefox. I was able to verify this by checking the About Firefox page. This is the third time I noticed this.
Yup,
apt install chromium-browsercallssnap install chromium. Looks like thunderbird is the same. There’s a fwupd-snap deb but fwupd seems to be the default.