As a follow on, I re-flashed to Firmware  Version 2.3.2.66 and Factory reset last week. removed all the manually assigned IP addresses and used the XR500 as it should be used.
My Son is Xbox Series X with Fifa 22 (wired) and with this firmware Version, very few disconnects, no speed up lag etc and Generally OK.
We have double NAT another wireless router of the XR500, just to provide wireless and parental control requirements and have disable Geo-Filter, but have used the XR500 QoS with Console added to list and seems to still work well, even after 1 week and stability is good
So looking forward to when Netgear / Netduma finally release a firmware that works well 
In a completely sane world, madness is the only freedom (J.G.Ballard).
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