Running the firefox install script in the docs, the download completes then I get

error: Uncaught (in promise) TypeError: stdout was not piped
    const stdout = new TextDecoder().decode(await proc.output());

System Info:
M1 MacOs 11.1
deno 1.10.3 (release, aarch64-apple-darwin)
v8 9.1.269.27
typescript 4.2.2