If OnyX is a must have for Big Sur, take a look at this from the developer and donate. If it is worth using, it is worth supporting.
For sure....I used OnyX quite a bit while sorting out a "slowness issue" in another thread. We all need to support our Shareware developers if we want to have such good software without needing to drop a C-Note on a giant corporation.
ryck
"What Were Once Vices Are Now Habits" The Doobie Brothers