Expose IFTT in KCSv3 as Switches in HomeAssistant

[twostar]

my HA already responds to power loss with a connected UPS and NUT. I just need HA to tell KCSv3 that there is a power loss, but I do not see any way to do that in the current IFTT IFs. Can I for example turn on a Digital Input from HA and that reflects in KCSv3?

You can do it but it's a bit messy, have HA set a KCS output, then use a relay to convert the wet-contact output to a dry-contact input so you can feed it back to a KCS input.  The real problem is that ATM there's no way to directly chain IFTTT rules without the output -> relay -> input hack, however there's an open request to add this that you could upvote.