I would like to add that a similar implementation from tailscale.
With Twingate (my preferred solution) they use what they call "controller". That would allow to acess resources on private networks, where the controller is deployed.

This is a critical feature for business customers IMHO
https://www.twingate.com/docs/how-twingate-works

Something like this would be extremely useful to me. Whether it's an actual Tailscale integration or a tailscale-like upgrade to the existing Proton VPN service.

I would love this. I had to switch to using Tailscale for everything, since android devices can't have more than one VPN active at the same time, unlike regular Linux devices. Being able to set ProtonVPN as an exit-node would fix this, since I'd be able to have access to my servers as well as have some extra security.

I noticed some people talking about the security of Tailscale, but that's really a non-issue, since you can self-host the management server. The underlying protocol is perfectly safe, and Tailscale offers a number of ways to make it even more secure if you need to.

Or add a tailscale-like feature to Proton allowing the same chaining through Proton rather than Tailscale

Yeah, that option can be really, really great for VPN

Tailscale is insecure if the coordination server is hosted by a third party. It effectively gives the coordination server access to someone's whole network.

With ProtonVPN, I hate that at home, from my Android phone, I cannot access my local network securely as I have to chose between Always-On VPN and 'LAN Connections'.

I think the above idea about using ProtonVPN with Tailscale exit nodes is based on a similar problem to me. I would suggest Proton looks at my root cause issue and cooks up a better custom solution.

I would love a solution to allow access to my home network (at home and away) with all my traffic routing through a ProtonVPN gateway. (Tailscale tech could be used as a starting point.)