i used the README
./configure && make && sudo make install-strip
trying on 2 different distros (mint/arch) and got them confused. ATM in arch linux and palemoon 27.9.2 i get
palemoon 27.9.2 starts with 9.54 from your source but with with errors above; and not with 9.52 from arch repos but that's not your issue. is the warning in quote of any significance?firejail palemoon
Reading profile /usr/local/etc/firejail/palemoon.profile
Reading profile /usr/local/etc/firejail/firefox-common.profile
Reading profile /usr/local/etc/firejail/disable-common.inc
Reading profile /usr/local/etc/firejail/disable-devel.inc
Reading profile /usr/local/etc/firejail/disable-interpreters.inc
Reading profile /usr/local/etc/firejail/disable-programs.inc
Reading profile /usr/local/etc/firejail/whitelist-common.inc
Reading profile /usr/local/etc/firejail/whitelist-var-common.inc
Parent pid 10333, child pid 10334
Warning: An abstract unix socket for session D-BUS might still be available. Use --net or remove unix from --protocol set.
Warning: /sbin directory link was not blacklisted
Warning: /usr/sbin directory link was not blacklisted
Child process initialized in 299.62 ms