It is your decision not to trust the FSF, but please note that 'Libreboot'
did not attack the FSF. The project's leader (Leah Rowe) made accusations
against the FSF, which have thus far not been supported either way.
Furthermore, please note that the firings from the FSF had *absolutely
nothing* to do with any part of Libreboot. Leah Rowe's friend was fired due
to unknown events happening within the FSF, which almost certainly had
anything to do with any GNU project.
In addition, the Libreboot software, being free, will remain just as
trustworthy as before (if not, then I'm sure we'll all know quickly- just
like the Ubuntu/Amazon saga). It appears it may separate into two strains
(Libreboot and GNU Libreboot), but this just means you can pick a side if
that should so satisfy you.
Otherwise, I suspect you may have trouble finding other free BIOS/UEFI
implementations- especially if you're on x86.