No, these sorts of faults can occur in any high performance chip. Intel is bearing the brunt only because they're the fastest. But Meltdown also affected an Apple core if I recall correctly and Spectre nailed them all.

This isn't as simple as "Intel/x86 sucks, let's go use SPARC". The causes run much deeper and the necessary fixes may or may not be architecturally elegant or simple.

RISC-V is far more promising than OpenPOWER ever was.

Last I checked, the Mill is vaporware. They have some interesting patents, a private simulator, parts of a compiler toolchain, and that's it. At least with OpenPOWER and RISC V, you can buy processors and even complete systems.

Are they alive? No news in the last six months…