Just upgraded from 6.8.3 with older nvidia plugin to 6.9.1 without any issues.
Upgrade steps for me were;
Backup flash + screenshot drive allocations
Stop all docker containers & disable autostart
Stop all VMs & disable autostart
Uninstall old nvidia plugin & ensure all other plugins were updated
Upgrade to 6.9.1
Reboot
Install @ich777's nvidia driver plugin, wait for install. Disable then re-enable docker.
Check GPU uuid in settings, confirm it was the same under jellyfin container
Reconfigure auto starts on containers and VMs. Start containers
......
Profit
Thanks to all involved for another smooth upgrade.