It's taken me months to finally get around to this, but on Saturday I sorted out my webcam from my EOS M6 Mark 2, a camlink, and a couple of lights. All bar the annoying 30 minute cutoff, it's working ok! Thanks to
@danmall, @drewm et al for the inspiration and blog posts!
And if anyone has the same set up, please do let me know why my picture keeps shutting off after 30 mins despite all the correct settings being applied (eco mode off, timer off, clean HDMI).