@mon_dieu,
Can you confirm same output for the status command as in the other thread ?
If so, the pihole-FTL
binary probably cant access that file anymore as its running with user "pihole" privileges now instead of root privies like dnsmasq
did before the Pi-hole version 4 update.
And that file is not part of the normal basic Pi-hole install.
grep -v '#\|^$' -R /etc/dnsmasq.*
?
EDIT: Owh first get it to work again with pihole -r
like @DL6ER instructed
EDIT2: I just read this bit that you could try: