I suspect it depends a little on how often you’re going to use it / need to swap cassettes if you go for the Kickr. Once a week isn’t too bad, daily would be slightly irritating, somewhere in the middle depends on your tolerance for faff.
We’ve got a Kickr and run a 9-speed cassette on it for that reason – we both a bike that can go straight on. It’s brilliant in a sturdy, smooth, low hassle sort of way and is superb with The Sufferfest in ERG mode and on Zwift.
I also have an ancient Tacx thing, a yellow one, and used to keep a trainer tyre on a spare wheel for it. The indexing wasn’t quite right, but near enough that a turn on the cable tension adjuster would bring it into line.
Have you considered gritting your teeth and upgrading your partner’s bike to ten speed? Logically you’d get the Snap, but if you can afford it, the Kickr is impressive.