Any with good hardware as long as you can switch to stable and community-made ROMs.

If you like reading books, comics, etc, maybe Librera Reader?

Dunno how it is on Google Play, but it's available FOSS and DRM free outside of it:
https://f-droid.org/packages/com.foobnix.pro.pdf.reader/

Linux systems are usually laid bare for people to tinker with, which for me is specially good if I see something I don't like, be it software, UI or UX.

Plus, most PC's I've seen from at least the past ~20 years can run Linux, so if I get my hands on a working PC, Linux becomes an easy choice.

Plus², Linux can be made very privacy friendly.

On the plus side, this gives people plenty of time to tackle their ever increasing backlogs, and also to give companies more reasons to put out a functional product in order to compete with all the kilometric backlogs people already have.

Same as the past 10 or so years, from what I can tell.

You also need to find instructions specific to your device on how to unlock the bootloader, and a TWRP specific to your device. From there, you do a clean flash through TWRP (erasing certain partitions and then installing the new ROM), and then, you should be good to go.

First, I'd suggest flashing a community system ROM. OEM systems are both very bloated, and stop being supported much earlier than community ones, so they're not ideal unless you need to use it with some banking app or the sort. And if you don't need Google's services (de-Google, anyone?), I strongly recommend going for a vanilla system instead of a Gapps one.

Now, as stated in MargotRobbie's comment, one good use is as a media player. If you can sideload stuff like VLC and Librera Reader, you should be covered.

You can also use it for some lighter gaming, if that's your thing, as there's plenty of emulators, wrappers and engine implementations for Android.

You can also use it for running servers, if you do this sort of stuff.

And if you like to test around with softwares, a spare Android device is pretty good to have.

Got a gaming laptop some months ago, and it is actually very powerful indeed. But it came with Win11 by default, only requiring the final setup. Now... How can a system lag a decent laptop so much.

Needless to say, it didn't take much for me to decide to swap for good ol' Mint Xfce, and even try out a few other Linux systems, and now, pretty much everything runs flawlessly, at most requiring to avoid using the ultra settings.

But indeed, Windows is bloat incarnated, and it only gets worse. So much so it even feels like Win10 on a VM can clog the whole system. Weird how that doesn't happen with Win7, no matter how long I leave it open on a VM.

Unsure what are those acronyms, but one text-only Linux program I can't recommend enough is ncdu: it helps managing storage in your system, as well as, indirectly, browsing your files.

I check sites that list hardware specs, and once I find a phone that seems interesting for an average price I'm willing to pay, I check places like XDA to know how much of a hassle it'll be to unlock the bootloader and add a custom ROM. And if modding the phone has too many/too big drawbacks, I return to the first step until I find a phone that seems good.