If a machine/server doesn't have built in IPMI, I am using an Adderlink Digital ipeps and control it that way 1). Apart from the built in RealVNC server, it also has HDMI video, USB and virtual media support among other things. I have no relationship with Adderlink, but I am a happy user of this product. Not cheap, but worth the price IMHO.
1) https://www.adder.com/en/kvm-solutions/adderlink-digital-ipe...