In addition, I pretty sure many European keywords can type µ by alt-gr+m, at least in Windows on my Danish keyword. Only know that because once I had a keyword were they actually had printed it on the key, just like they always do with € on E.
There's always character map which has this and like all others you can ever think of. A bit cumbersome, but at least one doesn't have to remember character codes and can search for characters by name.
"Let me google that" pulls out character map pretty poor UX if you ask me. Almost as bad for search ability as calling your product "go" or "cloud" or "driver" or any other one-word generic, hard to find even with contextual terms around it.