I recently got a PS5, its been great to upgrade as I though lagging was due to my PS4 being 8 years old.
My Ethernet speed on my laptop, during peak times as well, is hitting between 65-70 down & 18 up. However on on PS5 it is barely reaching 30mbs down 14 up at all times.
I am running a deco mesh system in the house, this is how my Ethernet connections are set up as well. Port forwarding is set up on the BT router for the PS, it did this automatically.
When I run a wifi test on my phone I'm pinging 65-70 and 18 as well. The deco system is working perfectly with everything.
It just seems the BT router doesn't like passing the much speed for my PS & deco
I have today (14:30) tried a direct wifi connection to my router (its the only device using it) and I got a 72 down and 18 up which is amazing but I won't know til later if it sustainable.
Cheers for your help in advance.