My bitcoint-qt client is crashing due to insufficient file descriptors repeatedly even after I set the ulimits to 65535 What are the exact resource requirements for a bitcoin-qt client.
this is important and hard to find information.
In virtualization world those things need to be understood. :)

I am running a KDE 18.04 Vbox on a mounted 1TB SSD share with 4GB Ram 4 cores.

Cheers :)
and the answer is....

if you use a shared folder on a VM the linux open file desc spec is irrelevant.
So I created a diskimage directly mounted in the host...
and voilà problem solved by avoiding the vbox host shared folder service indirection.
maybe playing with the vbox host config and system config would have helped as well.....