Turris Omnia 3.8.2 and Nexus 5x with stock 8.0.0 here. I confirm that the WiFi connection is unusable after a while, despite trying various combinations on DNSSEC and forwarding.
I am experimenting with a specific DNS assignment as workaround for the Nexus as described in https://forum.test.turris.cz/t/yamaha-receiver-problem-with-knot-dns/1304/23. I will have to wait some more hours/days to confirm that the promising results are not only due to a recent reboot of the smartphone.