AMD has the same problem (Inception). Predictive instruction pipelining makes timing and context separation harder. Even if you are on s390x or M1 it's not like you are safe either. This is a whole field of study.

In my mind the better mitigation is to put control over trusted code back to the user and to do that you have to add less-performant cores onto the die and force the operator to elevate (or not) to SMT.

Right now it's an all-or-nothing proposition for the whole board. I would like to think that you can take your untrusted code and stick it on the less-performy cores with the safer instruction pipelining scheme so an actual physical barrier exists.

If that was in the chip architecture, then it's up to OS vendors to surface it in a way that developers understand, and then down to the operator to decide upon configuration.

You are never going to get a perfect-solve from the chipmakers on this where the consumer has to do nothing.