Is it possible to use AirDrop and Sidecar with a mac on a VPN? I need to use a VPN on my mac from time to time. While I'm doing so, it interferes with  the ability to use AirDrop and Sidecar. My VPN has the ability to whitelist certain apps, so is there a collection of 'apps' that AirPlay and/or Sidecar uses?

I think Sidecar doesn't work with a wired connection when the VPN is on. I've tried whitelisting e.g. Finder but that's not enough, I'm not sure what else could be useful.
(This solved my similar issue with Airdrop, not tested Sidecar yet.)
I do not have VPN at router but on individual devices, so VPN broke my iCloud copy/paste and airdrop. It may be because they were not &quot;sharing&quot; the same wifi network anymore, as in, they had two different data tunnels, and the only solution I found was to deploy VPN at router or to turn off VPN.
I dig Mullvad VPN Mac app preferences, and found that there is an option to enable &quot;Local network sharing&quot; that allows local network access to connected devices. I turned it on and voila, I had my airdrop back. I believe that major VPN providers' Mac app has this function, and if you toggle this function, you can get your problem solved.
ps.: I strictly use Wireguard protocol, not OpenVPN. Not sure if it has anything to do with it, just saying...