Browsing Chromium Gerrit, you can find mentions of desktop-optimised Android builds which targets both ARM64 and x64:
- https://chromium-review.googlesource.com/c/chromium/src/+/5686301
- https://chromium-review.googlesource.com/c/chromium/src/+/5743054
- https://chromium-review.googlesource.com/c/chromium/src/+/5715668
- https://chromium-review.googlesource.com/c/chromium/src/+/5727183
They are also making changes which implies desktop-optimised Android is different from usual Android builds:
- https://chromium-review.googlesource.com/c/chromium/src/+/5718751
- https://chromium-review.googlesource.com/c/chromium/src/+/5685953
Moreover, they are experimenting with bringing extensions support to desktop-optimised builds:
- https://chromium-review.googlesource.com/c/chromium/src/+/5757985
- https://chromium-review.googlesource.com/c/chromium/src/+/5758420
Given recent news that ChromeOS is moving to Android stack, we could assume Google might be bringing Android to desktop in one way or another. I hope this is true, and I hope one day we'd see GrapheneOS for desktop as well.