Kotlin 1.3.40 experimental [OS] x64 compiler missing

where did it go,
did you drop it?

We build such artifacts via Excelsior JET which has been discontinued recently. Because of that, we decided to stop publish artifacts built with Excelsior JET but we still build them and if you need them – we could provide them manually. We understand that such version of our compiler could be useful and we are looking for alternatives.

Interesting. Have you tried Substrate? Are there any problems with it?

It could be helpful, keep searching…

Yep, Graal AOT is in our plans. We expect problems with library trove that we are using and reflection calls.