As someone who used multiple features of Keychain Access over the years, while it has a cleaner interface, I find Passwords underwhelming. BTW, Keychain Access lets me get at items in the iCloud Keychain with my login password. Unfortunately, as the update was supposed to be from macOS 15.8 to 15.8.1, rather than 27.0.1, I didn't make a bootable backup. Other than system files, my data lives on a separate NextCloud server (with off-site back-ups), so I normally don't worry too much when upgrading.

I've managed to reset the IRC password, however I have three critical notes with security question pairs for an airline and two financial institutions that I can no longer access.

I'm not sure what "forcing compile using clang20" means. In my case there was no difference between Apple clang from Xcode 26 and clang-mp-20. However, using /usr/include/mach/port.h from Xcode 16.2 got past the error.

Same here on Mac mini M1