steamcmd crashes with Ubuntu-focal?

Steps to reproduce:
```
docker run --rm -it --name test drpsychick/linuxgsm-ubuntu:latest /bin/bash
> linuxgsm.sh gmodserver
> ./gmodserver auto-install
# notice: steamcmd download of the game fails with thread errors or gets stuck, sometimes...
```

Tasks:
* check which distributions are affected and update this issue
* resolve when it's fixed