How hard, in theory, would it be to set up a Rpi4 as a thin client for RDP/VNC only, i.e. connect it by ethernet to a network but only allow it to communicate on the necessary ports for those protocols?
(it could be connected to the internet initially for setup potentially)
Not very. Add some iptables rules to only allow RDP/VNC, and probably DNS, and don't give the user root access so they can't change the iptables rules.
How hard, in theory, would it be to set up a Rpi4 as a thin client for RDP/VNC only, i.e. connect it by ethernet to a network but only allow it to communicate on the necessary ports for those protocols?
(it could be connected to the internet initially for setup potentially)