I saw this article on Tom's Hardware today. There is a community-based project called Windows Update Restored Currently, they have updates for Windows 96, 98, Me, 2000 and XP. They have links for Windows Vista and newer, as well as Windows Server 2003. This is very much a use-at-your-own-risk site, but I know a lot of people on here maintain old computers for many reasons, so I thought I would link to it.
https://www.tomshardware.com/news/windows-update-restored-site-provides-updates-for-classic-windows-versions#xenforo-comments-3813195
Derek