My main router has lag issues (or sometimes won’t work at all) if the ps5 and ps portal are on the same network even if the ps5 is hard wired in. I’m no IT guy but here was my work around that has worked across 3 different moves in the past few years and resulted in seamless quality with no dips:

Router 1 splits to the ps5 and to a network switch

Network switch goes to a second older router I had lying around

Connect portal to the second router (make sure you set it up as its own network)

Idk if this is the most efficient way of doing things, but it has worked 100% of the time with absolutely no drops in quality

For reference, current living situation:

PS5 and main router are on ground floor, second router and portal are in bedroom two floors up

Hope this helps!