Apple Devices app not finding iOS 26 update for iPad 8

I have an 8th gen ipad, with (only) 32 mb of storage, of which 25 mb are in use, and I can't (or more accurately don't want to) delete enough apps etc to update to ios 26. It's currently on 18.7. I have a windows 11 desktop and I have installed the apple devices app on that, to try and update the ipad, but the apple devices app tells me that the 18.7 on the ipad is the most recent update available. How do I get the apple devices app to recognise that there's an ios 26? (the update setting on the ipad tells me that ios 26 is available, but it can't download due to lack of storage}