The last time I have evidence of DNS resolution working on my OMV5 x86-64 system is a week ago when I updated to 5.5.8-1.
From OMV I cannot ping google.com, but can ping 18.104.22.168.
I have had multiple network configuration changes in the last couple of weeks which may have caused this:
I tried to create a network bond (as I had working in OMV4), however failed, requiring OMV-firstaid to restore network connection. I was subsequently unable to save my attempted change to my DNS address in the Network>Interfaces, however since the 5.5.8-1update I am now able to change it.
I have instead used my second interface for Docker containers, including Pi-hole, via a macvlan. Pi-hole is working properly for selected clients on my network, using as upstream servers Google and my ISP's. My router is also using Google and my ISP's DNS - not Pi-hole
My /etc/resolv.conf is an actual file (not a link) and lists my router as a nameserver, as does the Global DNS Server in resolvectl - the Link DNS server is now showing the change to my ISP's DNS server I made in the OMV control panel.
I do note I have a etc/resolvconf/ directory.
Any suggestions as to what to try now to get DNS working on my OMV system again would be welcome.