Badabinski

Wireguard was written with the explicit goal of having sane, secure defaults. I totally feel you w.r.t. openvpn or ipsec, since it’s easy to do something wrong. Wireguard is much easier because it simply refuses to give you the choice to do things incorrectly.

w.r.t. the certificate thing, you could set up a reverse proxy and do HSTS to ensure nobody can load up a rogue CA on your devices. HSTS has the issue that SSH has (trust on first use or whatever it’s called), but you just need to make sure nobody is MITM you for that first connecting and then you’ll be good to go. This would let you use a self-signed certificate if you do desired.

For people like me who lack context:

Authelia is an open-source authentication and authorization server and portal fulfilling the identity and access management (IAM) role of information security in providing multi-factor authentication and single sign-on (SSO) for your applications via a web portal. It acts as a companion for common reverse proxies.

rsync -avr --progress in termux or a file explorer app built on top of scp or rsync. It doesn’t work like your use-case, but I’ve been happy with it.