In settings >Timelines, there is a new option that allows to underline clickable elements. The option has been enabled.
https://storage.gra.cloud.ovh.net/v1/AUTH_91eb37814936490c95da7b85993cc2ff/tootfedilabapp/media_attachments/files/111/606/465/179/391/917/original/115da5d2b49e3960.png