I also have the same issue, with everything submitted to the repo's using the Artix Buildbot.
I've tried running the following, without success:
#!/usr/bin/env bash
rm -rf /var/cache /var/lib/pacman/sync/* /etc/pacman.d/gnupg;
pacman-key --init;
pacman-key --populate artix archlinux;
pacman-key --refresh-keys;
Only saying this because it means that it's definitely an issue with the Arch Buildbot's PGP key, and not with my or test4d's system(s).
Edit:
Output of the commands recommended by cat herders of linux for me is:
[adam-artix-laptop adam]# pacman-key --recv-key 0A3EB6BB142C56653300420C1247D995F165BBAC
gpg: key 1247D995F165BBAC: "Artix Buildbot <[email protected]>" not changed
gpg: Total number processed: 1
gpg: unchanged: 1
[adam-artix-laptop adam]# pacman-key --lsign 0A3EB6BB142C56653300420C1247D995F165BBAC
-> Locally signed 1 keys.
==> Updating trust database...
gpg: public key DB323392796CA067 is 3037 days newer than the signature
gpg: marginals needed: 3 completes needed: 1 trust model: pgp
gpg: depth: 0 valid: 1 signed: 12 trust: 0-, 0q, 0n, 0m, 0f, 1u
gpg: depth: 1 valid: 12 signed: 111 trust: 1-, 0q, 0n, 11m, 0f, 0u
gpg: depth: 2 valid: 105 signed: 36 trust: 105-, 0q, 0n, 0m, 0f, 0u
gpg: next trustdb check due at 2022-07-10
This does not stop the error.