Is it possible to use legacy 390.x driver alongside with current 4xx release? My question boils down to whether it’s possible to use GTX 580 together with Quadro RTX 4000 on single host, eg from within container or something like that (I’m interested in pretty much any solution as long as it doesn’t involve VT-d and GPU passthrough)
I don’t think so. In theory, you could rename one driver and then use the NVreg_AssignGpus= module options to bind them manually to the corresponding gpu but in practice you would run into collisions since the driver consists of 2-3 modules with dependencies using the same symbols. Using this approach, you can load nouveau on on gpu and the proprietary driver on the other but this doesn’t really has much to offer performance-wise.
If you’re going to use a PCI-E passthrough it must be possible if your guest has its own driver.
Having two different drivers versions on the host is impossible if I’m not mistaken.
You can find some helpful tips in the Arch Linux wiki.