iMac keeps changing host name...

Hey all, I have an M1 iMac connected to my network via Ethernet. Initially I disabled WiFi because I was only using the Ethernet connection and everything was fine. Trouble is I now have an iPad on a stand next to my iMac which I use as a second screen (with Sidecar) and for the detection to work you need to have WiFi connected on the iMac.

But when doing this the computer will randomly change the host name and put (2) at the end of it. It's very annoying and seems to be a problem going back over a decade that still hasn't been fixed by Apple.

Anyone got any tips for me to continue to run Sidecar but not have my iMac change host name all the time. Thanks.