A git bisect seems to suggest that https://github.com/go-ping/ping/commit/30a8f08ad2a9d0b88ca9c1978114d253f63748c3 is the commit which resulted in the regression in go-ping. Sadly that made it into the package that shipped with bullseye.
I can update the go-ping package to a newer version that resolves this bug, and bump a new build of smokeping_prober. Perhaps somebody with more free time can backport it to bullseye.
