Thanks for answer.
I have VM and on it work Accounting. Everyone has their own crypto usb key for work Internet-banking and etc.
We use second variant.Sorry if I suggested that you could easily change it your self, it's a variable in our code, we'll just need to reconfirm that increasing it has no impact (i.e., additional XHCI usb controller required, and thus a live migration change breakage)
For documenting purpose: the variable is located in PVE/QemuServer.pm around line 800, named $MAX_USB_DEVICES, you could edit /usr/share/perl5/PVE/QemuServer.pm and then restart pveproxy and pvedaemon, it's hacky I know, just FYI.
And you use SPICE USB for that, or are they keys directly passed through to the VM? In the latter case you could pass through a whole port and plugin a USB HUB there, that could avoid this too, just as idea.
As I understand it, in proxmox 6 version via USB HUB too limitation in 5 usb drive ?I just tried it with 6.0, we currently have the same limitation there.
I talked with a colleague and the limit is here to be able to ensure live migration works (after unplugging again), so we may want to make this configurable (so users can choose if they need more then a few).