It looks like @eSlavko just fond a bug in KiCad V5 in this thread:
I tried it and can confirm it is very easy to reproduce.
- Open a project in the project manager.
- Double click on the [project]-cache.lib file.
- Project manager freezes.
A “Loading Symbol Libraries” dialog is opened, but it makes no progress, and the dialog can not be closed normally.
As eSlavko is not very experienced with KiCad I am willing to make a bug report for this on gitlab (Already checked, I did not see this as an open issue), but because Linux Mint is not “officially supported” It would be nice to have some confirmation (preferably different OS’es) before I do so.
Version: 5.1.8-db9833491~87~ubuntu20.04.1, release build
libcurl/7.68.0 OpenSSL/1.1.1f zlib/1.2.11 brotli/1.0.7 libidn2/2.2.0 libpsl/0.21.0 (+libidn2/2.2.0) libssh/0.9.3/openssl/zlib nghttp2/1.40.0 librtmp/2.3
Platform: Linux 5.4.0-53-generic x86_64, 64 bit, Little endian, wxGTK
wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8) GTK+ 3.24
OpenCASCADE Community Edition: 6.9.1
Compiler: GCC 9.3.0 with C++ ABI 1013