I have a Raspberry Pi 4 running Home Assistant OS. I have several add-ons running. When I boot the pi, devices will connect quickly to my wifi. Over a few days devices get slow to connect, around 20-30 seconds rather than 4-6 seconds. If I reboot the Pi wifi connections are fast for a few days before having the same problem again.
I am running Ad Guard Home, NGINX Home Assistant SSL proxy and Duck DNS as well as others. If I stop these add-ons wifi connections are still slow. If I unplug the network cable to the Pi wifi connections speed up again. When I plug the cable back in, connections slow down again. Only a reboot restores fast wifi connections. Wifi internet speed is not affected just how fast a device connects to my wifi network.