Asklemmy

I hate to come across as an Apple shill, but specifically for tablets, I may reconsider them and look for an affordable used iPad somewhere. From my own experience, theirs is the only OS that is designed tablet-first and they accordingly have a larger ecosystem of apps that are tailored to that experience. I don't think you can find a more accessible tablet UX in the general consumer space.

Windows and Android tablets are fine, but you're going to have a lot of compromises. In particular with Windows, you're either going to get the x86 OS with short battery life, or the neutered ARM version that barely anything is compatible with but gives you a few hours more per charge. Android at least is more mobile-oriented and is built for ARM by default, but it makes no real distinction between phone apps and tablet apps, so most of what you'll get is phone interfaces blown up/stretched into tablet ones. Both of these OSes are also privacy nightmares, so pick your poison there.

There are some Linux tablets out there, too, but they've got the same core problem as Windows, where for tablet-first experiences you're looking at pretty small/specialized ecosystems unless you're up for building something yourself. Starlabs makes a tablet that you can put just about any major distro of Linux on, but it's also x86, and it ain't cheap. There is probably cheaper out there, but you're essentially getting what you pay for.