trace: warning: The option `fonts.enableDefaultFonts' defined in `/nix/store/1rp9mgpy83k4w11gi58hqfcqhk3nnahp-source/flake.nix' has been renamed to `fonts.enableDefaultPackages'.
You updated your nixpkgs input, which has renamed that option, just as the warning says. You’d do well to change the option in your config to the new name, as eventually this will become a failure.
You just updated with nix flake update, you don’t need to change the input URL to get a new nixpkgs commit. This is all normal so far.
Hm, yeah, sucks when that happens. Sadly I don’t think the module system is currently capable of telling you exactly where the offending setting is set. Some other module helpfully sets this setting for you, and for one reason or another has not yet been updated to the new name. This can be for one of two reasons:
You import a module from outside nixpkgs and this module has simply not caught up with the change yet. Remove external modules one by one and evaluate with nixos-rebuild build, then you should be able to spot it. Check with their upstream about fixing this.
There’s a module lurking somewhere in nixpkgs that the PR author missed while changing the name, and was somehow not picked up by CI. If so, you can try disabling stuff that looks like it may set fonts until you find it.
If you want to not get caught by stuff like this in the future, use nixos stable and check the release notes when you upgrade to a new distro version.