If it's not a link then open the tooltip on tap.

And I'm not sure it should be a link. Using the displayed time for a permanent link to a post - while ubiquitous - is a weird UI hack.

Long press brings up tooltips in iOS. Perhaps in Android too.

That's only if the text isn't also a link. For example, on hacker news, the time is also a link. So long press shows the preview of the link instead of tooltip on iOS.

Make it a “hidden” link or something like on discord maybe?

Edit — I’m not a frontend dev. I shall defer to their expertise in said matters.