I shouldn't rush that much to upgrade my Pi-Hole to the never v6 version after 1-2 day after it released in February 18th, just to end up brooking my existing setup. I had to start over since I was dumb enough to not make a backup of my existing working setup, I don't know what I expected. While the update was nearly fished the gravity updated failed and I had to stop the it with CTRL-C after waiting for hours to complete, it was stuck for some reason. After rebooting my pi the pihole service still started up but slowed down my pi and got completely unresponsive. I had run Bullseye on my Pi Zero W v1.1 board and either way I still wanted to upgrade to Bookworm. I had an older backup of my pi's sdcard with Bullseye and pihole v5 on it that I could flash back to use while I finish setting up the new image with Bookworm and pihole v6. I know I could avoid complicating things if I had another sdcard that I could use for the new image, not having to copy back and fourth different images while making lots of backups frequently of the new image after working on it for a couple of hours.
The only thing that made less painful doing it this was using pishrink that spared me hours whenever I needed to copy back the new image making it way faster then copying back 32 GB that takes a long time. I'm can't be happier that I found this nice tool that speed up significantly copying the images and swapping between the old perfectly working one and the new one until the new one was set up fully.
It took me days regardless to finish the new image because of lack of time to sit down and work on it until it's done, only doing small steps at a time. Now everything is working fine, I'm running the latest pihole version on bookworm for just about two weeks.
But probably I had to start from an fresh new install, because I tried upgrading from bullseye to bookworm and it wasn't end up well, probably there was lots changes between the two.