The main criterion to evaluate a phone should be how easy it is to install your own recovery and system. Pretty much all vendor-provided distributions from any major vendor (regardless of which country) are going to make decisions in the interests of the manufacturer (including violating privacy, making battery management decisions that are more about planned obsolescence than battery life, not letting the owner have root access to install a real firewall, etc…).

Xiaomi is perhaps the most often recognised Chinese vendor as being custom system compatible - at least they have an official path to root - but the official path to rooting your own hardware after you have purchased it is rather dystopian. It involves download a Windows-only tool (or a reverse-engineered third party tool) that talks to their servers, creating an account with them and handing over lots of PII. Then you have to “Apply” to them to unlock your own bootloader, and give a reason. Then they make you wait a variable amount of time (which is sometimes measured in weeks) between when the software first tried to unlock the phone, and when their system will allow you to unlock the bootloader. They will not reduce the wait time if you contact their support and beg nicely for them to graciously let you restore your system onto a new phone that you bought with your own money from them, replacing another identical model that broke. Eventually, after making you wait, when you try again after the minimum time, their system generates a certificate, signed by them, that will allow your phone to transition to ‘unlocked bootloader’ mode, and let you flash what you like.

As such, I’d not really recommend the Chinese vendors unless you find one that doesn’t make you jump through such ridiculous hoops. While I never recommend giving Google any of your PII, if you just want a phone to install your own system on, I’d recommend Google over Xiaomi etc… if within budget; they at least recognise that if you buy it off them, you should have the right to install privacy respecting stuff immediately (they do make you click past a warning that the bootloader is unlocked on every boot, but that is pretty minor and is two quick button clicks you anticipate in advance per boot).

One pro tip: Once you have flashed a custom system, get something like F-Droid installed as your app store, and install a good firewall from it (AFWall+ or similar; many apps you might install are not privacy respecting, and a firewall helps), and also battery management software (ACCA is good; manufacturers optimise for day-1 marketable battery capacity even if it will trash the battery within a couple of years that could otherwise last a decade; only using 5% - 85% of the manufacturer battery capacity, i.e. turning off charging automatically at 85% and shutting down if you hit 5% instead of 0%, will make your battery last many times longer for most of the battery life, and modern LiPo batteries last surprisingly well per charge to 85% if you aren’t running lots of software that is wasting battery on anti-features).