I just have an always on VPN so can tunnel back to my home assistant server; which can handle todos/reminders/calendar events. Quick messages to contacts I haven't considered.

I already use a VPN (Proton) so I can't VPN back to my home (i.e. Tailscale). A very unfortunate limitation of Android.

RethinkDNS has the potential to solve all my problems since it can do per-app proxies, however I've found that it doesn't work well with Proton (or possibly Wireguard as a whole) with frequent proxy disconnects, making it a very painful experience. Which is a shame because in some cases I value DNS filtering more than VPN.

Last time I tried, Android Auto refused to connect with an error message stating it will not start if VPN is active on the phone.