It looks like there is a revision 4 of this router according to the download on tp links website https://www.tp-link.com/uk/support/download/archer-ax55/
Version 1 has a Qualcomm chip that might be supported in the future
Version 2 has a Broadcom chip which will never be supported most likely.
It doesnt seem like a version 3 exist, how can I find what chip version 4 is using? Seems version 1 is several years old so it would be unlikely to find one new.
a) never buy a device, unless you can positively identify it as being fully supported, right now. Don't bet on potential future support, play it safe - there will be similar options that are sipported.
b) the FCC ID should provide you with photos of the internals (often blurry and bad quality, they are nevertheless a first hint, followed by checking the OEM firmware downloads).
GPL source code says it is kind of qulcomm arm cpu, includes some binary blobs to celebrate GPL.
You may try setting log level to maximum and capturing log from cold boot. It may disqualify hardware due to incompatible components before even attempting to open case and connect serial. After HW documented roughly either you take on porting OpenWRT, or we just leave it there as documented.