One of the things I always have to remember to do for Qgis is for each time I install a computer or VM is to change the default settings in /etc/security/limits.conf to allow a larger number of file handles. Otherwise Qgis can’t open a lot of layers at once.
Open this file and put the following at the end
* hard nofile 10000
* soft nofile 10000
Then after doing this you need to reboot the system. This fixes the crashes.