Posting this because I didn't see this anywhere despite waiting weeks for the v6 upgrade to settle down, and if you use the web interface to make DHCP reservations to make your network orderly then you may be sorely disappointed with v6:
The new interface for DHCP lease reservation is... well, not even an interface. It's just a read-out of a text config file. Management is much harder with this for most users, and it's nowhere near as easy to administer. Yes, there's a FR to get this done... which may never be done. Certainly not in my lifetime.
Literally the biggest feature for me (other than blocking) in pi-hole and now it's basically trash.
FTR I'm totally happy using text files for configuration, and have run my own linux server for 20+ years. But pi-hole's admin was usable by other members of my family... but a text config file isn't. Great for sysadmins, but not for non-technical users (such as my wife who is happy with a gui but would not make changes via SSH for instance).
Really think changes like this should have been highlighted to those who weren't using the beta - the new GUI was presented as being fully-featured but this got left out. The only experience I found of the v6 GUI before upgrading was third-party YT videos, and unfortunately this wasn't mentioned.. and I never thought it would be a backwards step!
But most importantly a heads up as I've (now!) seen threads on here and on reddit saying exactly the same. Forewarned is forearmed.