When Ubuntu Unity 26.04 was released, it was stressed that it was NOT an “LTS Release” because the developers were short-handed and unable to guarantee they could provide support it for five years. Instead they urged everyone to remain on 24.04LTS. I have my settings set to only alert me to LTS upgrades and to ignore the interim upgrades. The other day I started getting alerts that Ubuntu Unity 26.04.1LTS was available for upgrade. So what’s going on? Is it an LTS or not?
Can you provide a proof link where it was stated? Update from the previous LTS releases was never available on the day one. It is finally available now. That is how it was always working.
The situation with Ubuntu Unity (and Ubuntu Mate for pretty much the same reason) has been discussed here and elsewhere.
That said, the upgrade tools can’t distinguish a flavor that circumstantially isn’t a LTS (and the common base code is anyway).
So, you’re seeing the same message everybody else got as soon as the upgrade path was open. Just ignore it if you want to stay with Ubuntu Unity 24.04.