What gives with the Secure Boot certificates (2023) and Linux?

I've been reading about the expiration of the 2011 Secure Boot certificates today, mainly with regards to Windows OS systems. Many of those users are dealing with older hardware that will not be getting a BIOS firmware update from the PC/laptop manufactures to get those certificates updated to the latest (2023) versions. The big appeal of getting users onto Linux was the ability to use older hardware that Microsoft deemed incapable of receiving the latest OS installs and updates. Sounds great, but now I am reading this issue carries over into Linux. For so long, we've been told something like...