When I add a link in the description field, I can’t open it by clicking on it

Links should be automatically recognized in the description field editor. To open one, just click on it and select the first available icon:

Opening a link in the description field

You can also add links to cards using the Web Attachments power-up or an External Link field.

Adding a link to the Web Attachment field
Opening a link in the External Link field

Plus, links work seamlessly in checklists and comments too!