So its not a wifi problem, its a throughput problem. Don't forget FTTP is a contended service.
It's not a throughput problem because I can get over 900Mbps on Ethernet.
It's a WiFI bandwidth issue due to using the WiFi 5 standard.
No contention issues on the WAN for me.
Speed test on Ethernet to back this up:
I don't know where the throttle is, but it isn't a wifi5 bandwidth problem as your wifi sync speed is 866M.