You can sub to it, but it’s complicated. (Instead of accessing that community via it’s remote host instance, you currently have to access it via your own home instance (for example by searching for it there). Maybe this could be made easier if lemmy would automatically replace links to other instances with the equivalent internal links.
This post featured on hackernews argues that users should be aware that this makes your google account only as secure as your weakest device security and thus isn’t ideal for the average user: https://lauren.vortex.com/2023/10/10/dont-use-google-passkeys-now