Comment 14 for bug 1896443

I found the solution.

It solves many other problems as well.

do this, on your host system (rpi4 armv71 for me). Before building or starting containers...
```
curl http://ftp.us.debian.org/debian/pool/main/libs/libseccomp/libseccomp2_2.5.1-1_armhf.deb --output libseccomp2_2.5.1-1_armhf.deb
sudo dpkg -i libseccomp2_2.5.1-1_armhf.deb
```

see https://askubuntu.com/questions/1263284/apt-update-throws-signature-error-in-ubuntu-20-04-container-on-arm
for more details