Mysql: Any way to properly index 3 ENUM columns with the same options ? (A OR B OR C)

I have 3 enum() columns with the same option values inside.
I first tried to use the "set" datatype which originally was meant to do that (hold multiple values from a set) but it seems that datatype isn’t managed for 15+ years and isn’t even supporting an index.
Is there a nice way to index those 3 columns so I can use them in searched without destroying query performance ?

SELECT * FROM TABLE WHERE a=’x’ OR b=’x’ OR c=’x’

I thought about creating a virtual field which uses a boolean logic (&) on the 3 enum field-numbers and combines them into a large number but that’s quite a hack and not nice to maintain.

Has someone solved this sort of task elegantly ? (I do not want to use a support table and JOIN it, I want to stay with a single table)