Are you talking about lemmy links? If so, you can force an app to open them but it depends on your phone manufacturer and whether or not that setting is hidden. For Xiaomi, you need an app to access hidden settings so you can force your chosen Lemmy app to open all Lemmy links in-app
Try this guide (teddit mirror, libreddit mirror); look around for how people do this for Revanced because it’s a very common question that comes up and someone might have the answer for you.
Guide on how to set revanced as default system app for opening yt links through other apps
Posted in r/revancedapp by u/PsychologicalMix883 • 648 points and 174 comments