Do not limit only to those. Are quite expensive.
A device for using it with a bunch of bitcoin apps you don't need super-extra expensive ones.
In the range of 150-300 cuckbuck you can find quite good devices that can be degoogled.
Inclusive some old Pixels, LG, Motorola, Samsung etc.
People will need to stack more sats not to pay for fancy new phones.
Note that the Pixel 4a is not receiving more security fixes.
From the official list you can see that the pixel 5a is the oldest still supported.
At this point I think the oldest phone worth considering is the 6a as it still has a few years of security updates(until Jul 2027), whereas the 5a security updates end soon (Aug 2024)
Found one locally for ~300 EUR, thinking about buying it (still seems expensive, after I bought iPhone 7, which is my main phone, year or two ago for ~130 EUR :D ).
For the DIY people buying second hand phones I strongly advise to get it yourself instead of buying online so that you can make sure that it is possible to unlock the OEM. So many phones are OEM locked by telcos (e.g., Verizon) and Graphene OS cannot be installed on them. So better checking in person (procedure explained in the Graphene OS guide) or buy from @abhishandy who will do it for you (i.e., find the phone and install the OS)