I upgraded my kopia installation to version 0.18.2 on my Mac running under Catalina (macOS 10.15.7). But, when I launch kopiaUI, I get the message « you need macOS 11 and above to use this application ».
BTW, can you update the documentation (https://kopia.io/docs/installation/), it still refers to macOS 10.11 and above? (I do not know how to place a request on GitHub).