Thanks for the guide!
I've been running Blue Iris for years but just sort of set it and forgot it (with a few automations ) so this finally got me to go back and give it a bit of a play.
Running the wizard failed for me as I don't have any open ports, but using the Local Webserver URL works fine.
And tbh the Genbolt jpg URL is a pita as it needs to be authorized regularly, so this is much better.
Thanks again.
One other thing, for completeness, the thing that got me, back when I first started with HE. Setting up your Hubitat dashboard, this is for an Image template, not a Video Player template.