Not a problem, but have been seeing questions recently of people not being offered upgrade from 18.04 to 20.04. I thought these upgrades were offered back in June. I upgraded to 20.04 from 19.10 and this was offered back in May. Imagine that different versions paths have different schedules, but google does not help explaining(that I found). Does someone know the schedules?
Every release has it's schedule published a few days into the development cycle, eg. Ubuntu 20.04's release schedule https://wiki.ubuntu.com/FocalFossa/ReleaseSchedule was created on 2019-February-19, though was just a place holder until 2019-October-17 when development started. The LTS to LTS occur after the 20.04.1 in all ML & official documentation, without a more precise definition of what after means (but do you need it?)
After a release reaches EOL the
archive.ubuntu.com will be moved to
old-releases.ubuntu.com. Again the word is after, for 17.04 this occurred the following day-week (mirrors of course don't all clear out the same time..) but for most releases there is a far longer delay (17.04 was unusually quick).