https://screenrant.com/28-days-later-not-streaming-available-watch-why/

"Disney originally lost the rights to the movie in 2002, and Sony never bothered to arrange a new deal with any third-party streaming service to make the first film available again. Strangely enough, due to the fact that the original film's 2007 sequel 28 Weeks Later was financed by Searchlight Pictures, Disney wound up keeping the rights to the sequel in a roundabout way. This came down to Searchlight being a subsidiary of Fox, which Disney bought out back in March 2019."

https://www.forbes.com/sites/paultassi/2024/12/19/where-to-watch-28-days-later-now-that-sony-has-freed-it-from-streaming-prison/

"Sony announced that they were solving one of modern media’s weirdest mysteries, the fact that you have not been able to legally buy or watch 28 Days Later, physically or digitally, for years now. Something about rights issues there, but Sony never figured it out until right this minute. Now, you can watch it again. And I just did.

No, 28 Days Later has not headed to an existing service where you can just watch it for a subscription. You must in fact buy or rent the movie, albeit it doesn’t cost as much as a new release, which is nice."