  Long-period radio transients have unusual properties that challenge their
interpretation as pulsars or magnetars. We examine whether they might instead
be powered by primordial black holes (PBHs) making repeated passages through a
host star, thereby providing a signature of elusive dark-matter candidates. We
demonstrate that constraints derived from the transients' period and period
derivative alone already rule out this scenario for most potential host stars.
While white dwarfs may satisfy these constraints, they are unlikely to capture
PBHs in the required mass range.
