I'm putting my time into riscv nowadays. The breaking point for me with ARM was their move to UEFI a few years back for 64 bit.
And remember, as open as ARM is now, that can end any time. It's still a licensed architecture. There was a time when x86 implementations were everywhere, in the way that ARM is today. You can see how that went.
I like Power but they've always had the problem that they're hot and expensive and power hungry, and while that's fine in their target environment it's not where I want to be.
ron