I'm on the latest docker tag ( Docker Tag 2021.10 Pi-hole [v5.6] FTL [v5.11] Web Interface [v5.8]) and I have also added BLOCK_ICLOUD_PR=false in /etc/pihole/pihole-FTL.conf.
Not sure what has changed, the iCloud Private Relay is not working any more and it used to work and I would have a different IP address.
Help is appreciated. Thanks in Advance 
alright, i think i found a solution.
thanks to @ jpgpi250
If anyone having a similar issue, this worked for me
What changed? Can you confirm the line is still present in the config file? What you found is a mere workaround.
Now I'm having both the BLOCK_ICLOUD_PR=false in /etc/pihole/pihole-FTL.conf and a new file in /etc/dnsmasq.d/xx-NXDOMAIN.conf with server=/mask.icloud.com/ server=/mask-h2.icloud.com/.
Earlier with just the BLOCK_ICLOUD_PR=false in /etc/pihole/pihole-FTL.conf did NOT work for me.
Below is the configs, that is working for me rn,
^ just this change did not resolve the issue.
Yesterday there was an outage for iCloud Priavte Relay. There might have some changes involved which might have broken how pi-hole handles it. This is just a mere guess.
Source: iCloud Private Relay Down for Some Users - MacRumors
Why do you think so? We followed an official Apple document with the Pi-hole implementation. I'm not aware of any changes.
I'm not sure. It did not work for me unless I have created a file /etc/dnsmasq.d/xx-NXDOMAIN.conf with server=/mask.icloud.com/ server=/mask-h2.icloud.com/
and BLOCK_ICLOUD_PR=false in /etc/pihole/pihole-FTL.conf
Then after a restart of pi-hole and my phone I was able to get it working again.
What are you trying to achieve?
Do you want Pi-hole to block Private Relay or not? Because
Turns off Pi-hole's blocking of the special domains and allows Private Relay.
But
Blocks the special domains and turns off Private Relay
