How does the lack of thermald make it unsuitable? I run arch Linux and I've never installed nor used it (there's not even a package for arch in the main repos). Your firmware already knows when it needs to throttle.
AFAICT, what thermald gains you is a smoother degradation of performance; it starts throttling earlier and more gradually than would happen otherwise. It's not obvious to me that there's any actual benefit of this; thermal limits are what they are, and you pay the price eventually if you really need all those cycles. Whether my system is slightly slower for a longer period of time or much slower for a shorter period of time doesn't really seem terribly significant.
Oh, I'm preety sure that Clear is unsuitable for most Linux users, thermald included or not, for many reasons. Specifically regarding thermald, I believe most people want their fans to kick early on low RPM and wait for the CPU to heat up and then max the fans out. The reason I believe so is that the whole industry have invested and still investing huge amount of money and complexity in making that possible and that is the default behavior of all hardware. Almost. There is right now top post regarding 2019's macbooks not behaving that way and the frustration it cause users.
It's not that I think that Clear is a stupid unnecessary project or anything like that, it is actually quite interesting experimental work. But it an experimental project and most people doesn't want something that avant-garde as their daily driver.
If I disable speedstep on my i7 8700K and lock it at 5.0GHz, CPUZ shows it running at a steady 5.0Ghz. But my temps stay relatively low when little is running. Starting Prime 95 Torture Test though, it quickly heats up as you'd expect and cools back down when I stop the test. But the whole time, the frequency never moves from 5.0Ghz. Do you or anyone know what's going on there?
AFAICT, what thermald gains you is a smoother degradation of performance; it starts throttling earlier and more gradually than would happen otherwise. It's not obvious to me that there's any actual benefit of this; thermal limits are what they are, and you pay the price eventually if you really need all those cycles. Whether my system is slightly slower for a longer period of time or much slower for a shorter period of time doesn't really seem terribly significant.