The darwin/arm64 installer download is currently considered "highlighted", so it shows up in bold:
(It was made "highlighted" when Go 1.16 came out in CL 278787.)
But not yet "featured", so it doesn't show up as a dedicated box at the top. Given darwin/arm64 port is a first-class port, and a good amount of time has passed that M1 devices are more widely used, perhaps now is a good time to do so.
Or, is there any way to detect user's platform and use it to suggest the right one first?
To my knowledge, likely out of device fingerprinting concerns, browsers don't officially expose the underlying system architecture, so web pages typically look the same regardless of whether the user is visiting from a macOS device with an Intel or Apple CPU.
I'm aware there are some workarounds, like getting the device GPU vendor name and checking for a known substring that M1 devices have. An example of that being used is the VLC home page, https://www.videolan.org/, which changes its default download link using that heuristic.
So, I'm not sure that we should try to add automatic detection. If we make both downloads Featured, they should be equally visible and hopefully easier to pick the intended one.
Or is there any way to build a universal installer?
This is possible too, but there are some trade-offs. We've considered it around 1.16 release but haven't decided to explore it further yet. It's a big enough change that it should probably be a separate issue.