With the Quad G5 now back in working order after the Floodgap Power Supply Kablooey of 2020, TenFourFox Feature Parity Release "30.1" (SPR 1) is now available for testing (downloads, hashes, release notes). As noted, this is almost entirely a security update and there are no user-facing changes except to wallpaper crashes on Apple discussion pages, another instance of the infamous issue 621 ("Assertion failure: slotInRange(slot)") which affected LinkedIn and is probably the same JavaScript library getting, uh, linked into something else. Hopefully this gives me a little more to work with debugging it. Assuming no problems, FPR30 SPR1 goes live on Monday evening or Tuesday Pacific time parallel with mainline Firefox 85.

http://tenfourfox.blogspot.com/2021/01/tenfourfox-fpr30-spr1-available.html