Recently read about this one, it appears to be one of the more interesting forks of Mozilla Firefox. More knobs in settings, sidebar, keyboard shortcuts; among other things, there's a knob for tab bar below toolbars, some update settings controllable through GUI like in old Firefox versions (there's no "Never check for updates", but the option to choose to install them is there), JPEG-XL support enabled by default, knob for turning on userChromeJS script support...
There's also Web Apps feature, I guess equivalent to Chromium's "install website as app".
Available x86 and x64 builds for Windows, x64 and aarch64 builds for Linux and a version for macOS (guess whatever's current in the Apple world).
Homepage: https://floorp.app/en
Downloads: https://floorp.app/en/download
Installation instructions: https://docs.floorp.app/en/introduction/installation/