I just submitted a review request  for kcov  that I recently
discovered. It has no relation to Linux's kcov and is more akin to
lcov, except that all it needs is a binary with DWARF debuginfo
instead of requiring compile-time instrumentation.
I came across kcov when I was looking for a way to measure code
coverage in a Rust project and I'm impressed. It supposedly has a low
overhead, but so far I've been monitoring small single-threaded
programs so I can't really tell. I haven't tested python and shell
support, although I have cases where it would be relevant, but I don't
have time yet.
I have been using it for a year now, and the only problem I had was to
upstream aarch64 support! (or technically write the patch)
Since it's currently not easy to run the test suite at packaging time,
and since the test suite is not really arch-aware anyway, it would be
great if someone with hardware could give it a try on architectures
other than x86_64: