Linux Onlyoffice Docker scripts are available for download. Are docker containers tied to a particular CPU architecture (IA64 vs ARM)? I would like to run Onlyoffice on an ARM platform (Raspbery Pi 4 or similar SBC computer).
TL;DR your idea won't work, for several reasons.
In general, yes, docker images are tied to CPU architectures. It is probably possible to run docker under a CPU emulator but you most likely won't be happy with the performance.
Some docker images can be built for different CPU architectures using very slightly modified Dockerfiles, just as you can build binaries using Makefiles. This works best if a corresponding base image is available and the Dockerfile just installs and configures packages from the distro's repository.
In your specific case, there only seems to be an amd64 docker image available. I don't know the software, so can't say whether it would be possible to build an image if you had the Dockerfile and other files needed to build.
However, given the resource requirements stated, an arm-based SBC may be underpowered for this application.
If you calculate the value of your time, spending some money on a suitable small PC would likely be the most economical solution.