Worth noting that Nvidia only intends to open source the kernel driver. This is only half the driver, as a userspace blob will still be required, and that will remain closed and proprietary.
I’d start with checking logs with journalctl as a privileged user. If the device disappears, there should be logs about it. Maybe that will point the way.
From West to East: Not the usual road traveled
Hard to know. Will the interface be specific to driver versions? Will it require an updated kernel driver for each userspace driver as it does now? I don’t know that we have the answers.