Earlier quoted context omitted.
I've got Ubuntu 22.04 lying around that still update because they are LTS. Ubuntu has a well publicised policy for releases and you will have obviously read them. Try do-release-upgrade. You also mention "OS supplied from a vendor with extensive customization. Apt was dead." How on earth is that Ubuntu's problem?
Isn’t Ubuntu basically killing apt? My Ubuntu became unusable because it kept insisting on installing a snap version of Firefox breaking a whole bunch of workflows. I do want to try a RH based OS (maybe Fedora) so they don’t keep changing things on me, but just where I am in life right now I don’t have the time/energy to do so, so for now I’m relying on my Mac. Hopefully I can try a new Linux distro in a few months,…
(I run Void myself, and stay merrily away from all these complications.)