Is the issue the Qualcomm drivers (or lack thereof) or a lack of developers that have time or know how to work on it? Mostly curious, looking for ways to help...
ipq8071a and ipq8072a are part of the same target, so any improvement for the ax3600/ ipq8071a directly benefits other devices of this target as well. However additional steps will be needed to support the other family members (frequency/ voltage points, etc. - the ipq8071a is a stripped down and downclocked entry level variant of this SOC family), so it's not a trivial device addition. Chances for the non-a variants of this SOC family are not looking great though (apparently not supported by ath11k).
While ax3600 support is actively being worked on again (and starting to look rather promising), it's not quite merge-ready at this point and still requires further development - follow the ax3600 thread for the details.
Which hardware is best supported generally and most likely to be the first one out with working AX in OpenWrt? I know various progress has been made but I really like the R7800 AC router since it's so easy to work with from a user perspective, any AX device like that might get support in the near future?
Yes, but while the AX3600 is still rather experimental the E8450 got merged a while ago (albeit past the 21.02 branching so it is only available in snapshots so far).
BTW: I do actually have both of them running in my lab quite nicely.
Really? A non-UK version for EU?
Where? can you provide a link? (So far I have only found the UK version, which I suspect to have the wrong power plugin)
Hagglezon lists Belkin RT3200 on amazon.co.uk for 79gbp (about 92eur) but because UK is outside of EU, getting it to Germany or Ireland or anywhere else would probably incur some cost. amazon.de and others have it for around 150. Linksys E8450 seems non-existent in Europe (if you find it, let me know and post a link).