Test elsewhere, and see if the issue persists. If not, the problems are seemingly isolated to your local wiring or your local boxes including the Asus gear, or ISP connection.
From what you report, -82 dB is deep down into the range with packet loss. Preferred is -65 dB or stronger, with -70 dB being considered marginal. (This decibel measurement stuff is also log-scale measurement too, so the difference in strength is way more than might seem. A tenth of the signal strength is -10 dB, a hundredth is -20 dB, and a thousandth is -30 dB. Signal drops fast.)
If the Wi-Fi wired backhaul is somehow also not working, there are seemingly larger issues with the local network.
In an inauspicious turn of events, went looking for Asus firmware and doc, got a few pages of data from Asus, and then got:

PS: If Private Relay is off everywhere, there’s no need to prepare for it.