Which one would you go for ?
They serve completely different needs?
As I understand it you would use Inertia if you want to use a classic frontend framework like React or Vue. And you use HTMX when you don’t 
I thought HTMX is also for SPAs, partially.
I am currently using AlpineJS as a jQuery replacement.
Clearly HTMX for me.
The killer for me is that I don’t see any evidence that InertiaJS provides support for websockets.
But even if that weren’t an issue, I don’t see where InertiaJS reduces or removes the need for me to write JavaScript code, or eliminates any of React/Vue/Svelt from the mix. From their docs:
Inertia isn’t a framework, nor is it a replacement for your existing server-side or client-side frameworks.
So I can see where someone already familiar and using React or Vue might want to add this to their stack.
Or they can get rid of all that and go with HTMX.
Thanks for your feedback, Ken, means a lot considering I wanted just some DIVs rendered partially and may be not the entire page.