How to use a formula column in saved search as an available filter (not criteria)?

SA 18375 might help

only the first formula of each type (text, currency, date, etc.) in your results set can be used as an available filter. Just select, e.g. "Formula(Date)" as a filer and the first formula date in your results will be available. If you want to formula(date) results in your filters then you'll have to get creative.

@SRP-curious tried this as you said and yes we can add formula column as filter but doesn't seem to work properly (but yes, it shows in the filter area) because no search result when filtering an obvious result

hmm that's mysterious. post some screenshots?