Comment by avidiax

I'm using the Monoprice multiviewer. It negotiates HDCP without a display attached. Other than being a bit big and expensive, and being unable to strip HDCP, it's a good solution.

I found the same device in generic packaging on AliExpress, but haven't had the chance to order that version, yet.

There are lots of professional SDI converters and such, but they are either $3k+ or "call for price".