I confirmed that the problem was in the gcrypt. More precisely, disabling SSSE3 fixes this issue (echo intel-ssse3 > /etc/gcrypt/hwf.deny).
The Virtualbox (running on Windows 10) was using software virtualization ("execution engine: native API") instead of VT-x - this might be the root cause (i.e. bug is in Virtualbox), but I'm helping a friend and don't have direct access to that PC, so can't test what's blocking VT-x. Hyper-V and WSL are disabled in Windows features, the person hasn't checked whether VT-x is enabled in BIOS yet.
Here is apport stuff, and there are more news.
I confirmed that the problem was in the gcrypt. More precisely, disabling SSSE3 fixes this issue (echo intel-ssse3 > /etc/gcrypt/ hwf.deny) .
The Virtualbox (running on Windows 10) was using software virtualization ("execution engine: native API") instead of VT-x - this might be the root cause (i.e. bug is in Virtualbox), but I'm helping a friend and don't have direct access to that PC, so can't test what's blocking VT-x. Hyper-V and WSL are disabled in Windows features, the person hasn't checked whether VT-x is enabled in BIOS yet.