I'm new to Linux but with some time I was able to get pihole working on a pi zero with Buster. After the update to 5.1 it stopped blocking adds but the web UI was still working. Looked though the documentation to see if I could find a solution and didn't find a trouble shooting section so I came here. Before I posted this I fallowed the recommendation of looking at other post to help me find a solution and when I tried one it just made things worse so now the web UI does not work.
I am writing this to say at one point I was seriously thinking about donating to the cause but when you have a WORKING product that fails after update, why would you? Do not treat this as a support question, I will just format my card and start over from the beginning.
After 5.1 is installed and working I will donate $5.00 for every 5.x build that works after the update without issue and I'll donate $10.00 for every successful new build i.e. 6.0. The first time pihole fails to block adds after an update from a working system my donations will stop, good luck.