Those old Dell Rxxx servers will make you poor with the amount of power they use. If you are going to self host, consider a mini pc, you can get one that can easily handle a witness for a couple hundred dollars. If you are determined to host yourself. A typical mini pc is 6W to 20W compared to 200-500W of a Dell server.

This should handle a witness no problem, I have one with 3 VM and 60+ docker containers running in a proxmox cluster and the power is around 11W.

Once the lite node functionality is more officially released, it should be even easier.