I have clouds but haven't tried alt firmware yet. I'm still wrapping my head around the factory one. There were some early serial numbers where installing any alt firmware could brick it IIRC but best get better info than what I remember. I would ask either in the Clouds thread on muffs - https://modwiggler.com/forum/viewtopic.php?t=127999 or on the Mutable forum - All Discussions - Mutable instruments' users community

I'm pretty sure there's a way to reinitialize the factory firmware if your'e worried about installing alts.