Not intentionally.
I intend to use WireGuard for outgoing traffic where that is suitable. I was mislead by the description of NAT-PMP into thinking that it might be possible to port forward back through the same connection. You have confirmed that it is NOT possible.
A VPN connection isn’t necessarily required on the incoming traffic. The incoming connection to Home Assistant can be secured by TLS and Let’s Encrypt over an unencrypted connection. Port forwarding is needed for this to work. I think the outgoing and incoming connections need to leave and enter the router using the same IP address otherwise DuckDNS with Let’s Encrypt won’t work.
I will look into Back To Home (BTH). I have installed the app on my mobile running GrapheneOS (I think it was flagged as “Early Access”?). I run Proton VPN but I may be able to configure BTH by using split tunneling to exclude my router’s IP address (192.168.199.1) and the BTH app from the VPN tunnel. So far, I haven’t been able to connect …
You have answered the question in the subject with a definite NO. Many thanks.