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.
I was commenting on this thread, where the commenter said:
"This looks awesome. I was looking for a solution like this last year. I budgeted a few hundred bucks but couldn't find anything."
So I only wanted to point out that there are good solutions out there, even though they might not be cheap. The solution have saved my bacon, and has been worth the money.
Looking at the original project, authentication, mouse support and audio are not supported (maybe in the future?), so if those things are important; a solution like the ipeps might be worth it as well.
1) https://www.adder.com/en/kvm-solutions/adderlink-digital-ipe...