Pass USB Device to LXC

Hello All.
I am on Proxmox V7.3-6. And I want to pass a USB Device on an unprivileged Ubuntu20.04.5 LTS LXC.
The USB device is a USB adapter to read my SmartMeter:

root@proxmox:~# lsusb Bus 003 Device 002: ID 10c4:ea60 Silicon Labs CP210x UART Bridge

I followed several instructions on the net. Unfortunately this does not work properly.
The most promising seems to be this tutorial:

https://www.schreiners-it.de/proxmox/usb-geraet-in-lxc-container-unter-proxmox-7-1/

But it...

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