I think it's generally true that Arm is more efficient and better for the environment.
There are 3rd party Arm images available and I'm running instances with these on AWS and Oracle, but they are not updated as frequently as the official images: https://hub.docker.com/r/masquernya/lemmy/tags
I know if I'm asking I should be ready to help, and I am. But this isn't something I know how to do.
You read the Dockerfile https://hub.docker.com/layers/masquernya/lemmy/0.18.2-linux-arm64/images/sha256-f1501bab2574cf371673d0926fdecd5b61e00d77e637ebc4f43a31ecbc029270?context=explore
To me the first line is pretty opaque
Maybe that hash lines up with a version of Lemmy, otherwise it's just a hash of a mystery block of files that could contain anything.
Here's an example dockerfile I wrote (for a different project) that's a little more transparent