do some shell games with various NATO F-16s by painting Ukrainian roundels on them as “tribute livery” and swapping them between various Eastern European NATO airfields and some western Ukrainian airfields
fly sorties from western Ukrainian airfields to plink targets of opportunity
use F-35s and B-21s as deniable + low-observability surveillance and ELINT platforms, backed up by AWACS and JSTARS and globalhawks (and whatever else we have these days)
Don’t even have to use F-35s directly.