I want Google to index the content in the link format domain/u/username, what should I do?

Help me index slug into username of source code?

I want to open index for this slug domain like this example: https://domain.com/u/toannguyen/activity (example link), what do I need to do in the discourse source code?

Currently, when I submit this type of link in Google Search Console, it says it is blocked from indexing. Hope to get help?

Thanks team so much!