Following the Linux install instructions causes the below error:
W: GPG error: https://apt.sumocli.app stable InRelease: The following signatures were invalid: EXPKEYSIG A9A6C1C7A8A9D508 Kyle Jackson <[email protected]>
It seems the key here is indeed expired:
$ curl -s https://apt.sumocli.app/public.key | gpg
gpg: WARNING: no command supplied. Trying to guess what you mean ...
pub rsa4096 2021-11-18 [SC] [expired: 2022-11-18]
2279C6441737217E049EA503A9A6C1C7A8A9D508
uid Kyle Jackson <[email protected]>
sub rsa4096 2021-11-18 [E] [expired: 2022-11-18]