I have been working all day with Claude in getting OTA setup on my Windows 11 PC running Arduino IDE version 2.3.8. Could never see the Wifi port. I downgraded to version 1.8.19. OTA worked good. This PC was on an Ethernet port using a static IP pointing to Google DNS servers. I have two Windows 11 laptops that are on Wifi. Version 2.3.8 worked fine with OTA. I went back to the PC and changed the two DNS entries to what DHCP assigns - one was to default gateway on Internet router (box that also has the Wifi AP) and the 2nd one pointed to a Centurylink cloud DNS server. OTA now works.
Probably the issue is not DNS resolution in the usual sense. OTA discovery in the Arduino IDE uses mDNS via Bonjour, which relies on local multicast, not external DNS like Google.
The DNS change itself is almost certainly incidental. mDNS does not query external DNS servers, so pointing to Google DNS versus router DNS should not affect OTA visibility.
What likely happened is that the static configuration on the Ethernet interface put Windows 11 into a state where mDNS discovery was not functioning (Windows network profile may have been set to Public, which restricts multicast and device discovery or the interface may not have been correctly registered for multicast or discovery services or misconfigured due to the static setup).
Switching back to DHCP-aligned settings likely forced a full reconfiguration of the interface, restoring correct multicast routing and service binding.
My money would be on the change restoring a valid local network configuration and re-enabled mDNS discovery, rather than DNS being the root cause.