Install

$ doas rcctl enable xenodm
$ doas rcctl start xenodm
$ doas pkg_add tigervnc
$ vncpasswd
$ vncserver

You want to use a vnc viewer like ssvnc to connect

WARNING: This setup has zero security. Everything you type including passwords can be keylogged. Someone should research how to set up SSL or a howto guide for how to tunnel it over SSH.