I did a fresh install of OSMC with 2021-08.1 on raspberry pi 4.
I had some issues installing docker containers becouase the dpkg achitecture says its armhf instead of arm64/aarch64.
Changing the repo an install for docker in apt fixed. But would be nice to have this correct by default
The Pi 4 OSMC image is multi-architecture, like the Vero4K/+: user space is armhf and the kernel is arm64/aarch64.
dpkg runs in user space as a 32-bit armhf binary and, AFAIK, the architecture is built-in to the installed package. So the “foreign” architecture is arm64, as running dpkg --print-foreign-architectures will confirm.