Microsoft expiring SHA-1 certificate at 9th May 2021 (Tomorrow)

Archive it all. I suspect in a few years they will just delete these old updates and claim it's for "security reasons".

You are not correct about SHA-1 Windows updates, those were already discontinued in July 2020:
https://support.microsoft.com/en-us/topic/wi…8b-139ce5c709af

The impact of this specific expiration event seems to be limited to some annoying pop-ups:
https://support.microsoft.com/en-us/topic/kb…fc-6dedef110e6b

Also worth noting this is a normal process for anything that uses TLS... Root CA's tend to be signed for anywhere from 10 to 30 years generally. Eventually those will expire and unless they are re-signed with root CA's that are trusted by devices (Which wouldn't happen for very old updates that aren't intended to be used) you'll get a warning that the certs aren't trusted in the same way a self-signed certificate would be (Though a slightly different error message).