Upstream stated they have no intention or capacity to maintain the legacy gnuradio 3.8 branch.
This git package does not provide 'gnuradio38' [a], so it has no dependents, only the latter does.
But both this and that package fails to build.
The few dependents of 'gnuradio38' are all dead and fail to build as well, or some of them actually have upstream updates or third-party forks that work with gnuradio 3.10.
So keeping this package is completely superfluous in my view.
[a]:
https://aur.archlinux.org/packages/gnuradio38?all_reqs=1#pkgreqs