Why, it should be supported. But you have to ask the fork developer on his blog.

TenFourFox is or rather was a third-party project fork of Firefox in their effort in keeping Firefox working with the then already old Macs on Mac OS X v10.4 and the Power Macintosh. Mozilla had nothing to do with this project. https://github.com/classilla/tenfourfox/wiki/ZZFPRReleaseNotes32 from https://www.floodgap.com/software/tenfourfox/ <blockquote>TenFourFox is not an official Mozilla product and is not a Mozilla-maintained build of Firefox.</blockquote> Mozilla dropped support of PowerPC looooong ago ([https://website-archive.mozilla.org/www.mozilla.org/firefox_releasenotes/en-us/firefox/4.0/releasenotes/ Firefox 4.0 released March 22nd, 2011 dropped PowerPC]) which is why the TenFourFox came about to keep Firefox running on those ancient systems for some more years. Right now the oldest macOS that Mozilla still supports with Firefox is macOS 10.12, 10.13, 10.14 with Firefox 115 ESR. https://support.mozilla.org/en-US/kb/firefox-users-macos-1012-1013-1014-moving-to-extended-support Firefox 78.15.0esr was the last to still support macOS 10.9, 10.10, 10.11. Before that Firefox 45.9.0esr was the most current you can run on the ancient macOS 10.6, 10.7, 10.8.