Luckily I can get the full speed using a newer device like my latest Asus zenbook or my wife's Samsung phone. But my Honor phone is terrible on both 2.4 and 5ghz.Guess it depends on the hardware. I have my main deco M4 connected via a switch that is wired with cat6 30 meters to my Asus AC86U router/hub. Both Deco's are cabled and set as access points (as tplink still haven't released a router function with the ability to switch off dhcp). I have 300/30 fibre. Can easily get 280 or so on the 5ghz within a couple of metres from the main deco. BUT the 2.4 is always terrible so I have that switched off and use a wr941hp and archer c80 for the 2.4 network which is really disappointing I couldn't use the M4's for a good 2.4 network. Wanted to tidy up the devices nit having to add more!!

@Emboss64 

After experiencing slow speeds I just switched the ethernet cable to a different port on the router and it solved the problem