Yeah, to reiterate, my kindle issues are not with my kindle device or the application associated with it - I use it happily on a Windows pc (mostly), an Android phone, an ipad and a paperwhite kindle device , and I really like the multiple device synchronisation feature. The collections feature I also find useful for aggregating subsets of my kindle library for different houehold family members.
No, my kindle issues are all to do with the enforced limitation and marginalisation of available content between separate Amazon marketplace entities and apparent geographical boundaries. There is no consistent universal availabilty of kindle content, nor is its pricing universally uniform.
I don't know why this has to be the case in 2023. I suspect some of it harks back to the 'good old days' of different geographic regional market rights for physical books, and is now largely irrelevant. Yet still it lingers, like a bad smell.