You seem to be unlucky and encountered some race condition as libvolk1.4, gnuradio 3.7.12.0 and the rebuild of gqrx-sdr against gnuradio 3.7.12 transitioned from unstable to testing.
I did need to fix the desktop mime install and iterate on gnuradio uploads, which I think got the libvolk auto-transition logic out of sync. But today I see your bugs, but I get home and update my testing box, I see a consistent set of packages updating, and it left me with a working gqrx. So, I am unable to reproduce what you saw. I do hope a quick update and upgrade of your testing box brings you back to a working setup. At this time Debian's gnuradio is a bit ahead of upstream stable releases, as I have included Qt5 patches from gnuradio development in order to meet Debian's goal for Buster to remove Qt4. Since it may be a while yet before a gnuradio 3.8 release, it seems useful to backport 3.7.12.0 for stable Debian users. gqrx update coming soon, thanks to Alex for making things better. -Maitland
