Currently the only Filter logic operators for multi-select fields are contains all and contains any.
Similarly with single-select fields, there is no logic operator you simply check the ones you want to include and leave unchecked the ones you don’t.
This creates an issue when the list of possible values for that field grows but you still only want to exclude only certain values because someone needs to remember to add those new possible values to the filter.
IDEAL STATE
Ideally we’d be able to Filter projects where field x is not equal to y or multi-select field a does not contain b.