Hi @Bund1984, additionally just for our context (apologies if you already posted these and I missed it)
Have you been playing the same Fifa version/EA servers and its only just recently started lagging for you in recent weeks? I can see you started posting here just before Xmas, has it been a long running problem even before that?
Did you have the problem before starting to use Internet Optimiser/DumaOS?
Does the lag consistently happen at particular times of day, eg. evening but not in the morning
Do you do any other online gaming from the PS5, eg. Is this just a Fifa thing?
With the Connection Indicators on, and your suffering lag, approximately what milisecond (ms) levels is the game reporting? (I'm not a Fifa player, but checking around you can turn these on at Settings > Game Settings >Visual >Connection Indicators)
Because you only have a couple of other devices on your network, and you have a pretty healthy looking high speed connection. I think its unlikely that your ongoing Fifa/ping issues are always being caused by local congestion. DumaOS/Internet Optimiser and the prioritisation functions, primarily help where there a many devices in a household fighting for the use of the internet, so I think its unlikely to be your ongoing problem. So things I'd suggest:
Ruling out that DumaOS is not actually contributing to the problem. Use MyTelstra to deactivate Internet Optimiser temporarily, then reboot your Gen 3 Smart Modem to ensure all has cleared - and play, did your lag still occur? If still occuring, re-activate Internet Optimiser
Ruling out wireless as the cause. Can see from a previous post, your already connecting the PS5 via cable.
If your ping time is consistently high, rather than spiking up and sometimes going back down. You could try using Geo-Filtering, so that you limit Fifa to only connect to Australian based servers (if their available).
Might also be worth posting on the EA forums if havent already, as it seems there has been some similar recent reports following updates, of previously satisfied players now suffering lag on PS5: https://answers.ea.com/t5/Technical-Issues/Fifa-23-PS5-connection/td-p/12209290
Hope that helps - and do let us know if disabling Internet Optimiser made any difference.