The R3 isn’t really powerful enough for that.

On small x86 routers you can install Opnsense or IPfire which come with some non-router software to run a reverse-proxy or so. IP fire also allows to run full VMs, but the more advanced features are pretty limited.

Some people also do the reverse and run a full OS on them and then virtualize Opnsense and directly pass through a NIC to that VM.