A Mac OS ARM build is not the same as a Linux ARM build. I would guess that at some point in the not-too-distant future, the Mac build will be a fat binary. But this thread is requesting a Linux ARM build, which is another thing entirely.
There are two costs to a new Linux ARM build. The obvious cost is the work required to port the existing Linux release to ARM. This may be little work, or it may be a great deal. I doubt that the existence of a Mac ARM port would make it much easier, because if there’s ARM-incompatible code in the code base, then it’s probably concentrated in the platform-specific parts anyway.
The second and much larger cost is that of maintaining, building, and testing a new build from now until forever. Only the Sublime team knows (or can guess) what the added workload would be, and only they can determine whether it’s worth it. Any work spent on a new build type — present or future — must inevitably come out of work spent on other features.