Curious; given that ARM Chromebooks are nothing new, I'm surprised that it took them this long to ship it to other Linux distros.
Chrome had no official arm64 build. There are distro specific builds from debian, fedora etc for arm64 chromium, but google had no official arm64 build.
There were actually some paid services that provided a distro-agnostic chromium arm64 builds mostly targeting people running puppeteer on AWS ARM lambda. You can see some discussion here https://github.com/alixaxel/chrome-aws-lambda/issues/241
edit: I think I replied to the wrong comment.