This doesn’t paint a clear picture.
There are two versions of Waterfox: Classic, based on Gecko 56 that has backported security patches (but is not recommended to be used unless you are desperate to use XUL extensions) and the 3rd Generation (G3) based on ESR releases.
Waterfox Classic is based on XUL and while we back port security patches as best we can, I always try motivate existing users to migrate to the newer versions. I’m not going to force an upgrade on Classic users as it will break their current setup and instead leave it their choice.
We follow the ESR release currently for “current” versions (the default download on the website) and since ESR78 didn’t support ARM on macOS there were no builds for it.
Now that we have the beta out for the ESR91 version, ARM support for macOS is available:
https://github.com/WaterfoxCo/Waterfox/releases/tag/G4.0.0b2
I’d like to think that Waterfox G3+ does fit in your criteria.