My first problem, which is likely due to the gradual shutdown of Antegros. When doing an upgrade just now, I get an error telling me that the package “quazip” is corrupted or has an invalid PGP signature.
I learned earlier today, that this specific package is in the Arch repo AND in the Antegros repo, and the Antegros repo takes precedence.
Solutions: Figure out how to force getting the package from the Arch repo (not a great idea), or uninstall any packages which depend on quazip. Fortunately the list is short and I removed krita (for now) and the upgrade proceeded normally.
In the mean time, I have other computers on which I have keepassxc, which also depends on quazip. For now it seems that I am trapped until or unless the short-timers here fix quazip in the Antergos repro.