Thanks for doing the research! 👍
Just to add some information: I bought my HP EliteDesk machines for less than €100 each, and I've found HDMI Flex IO modules on eBay for around €22.
So these machines can be a very affordable option, especially if you already have one.
I'll share the eBay links below. Of course, we still need to confirm which HDMI module version works with the 705 G4 SFF.