It’s still possible but that requires a few steps to works.

If you’re using the official YouTube app, you can press the three vertical dots button on the website, you should have an option called “Open app”.

If you’re using ReVanced/Vanced, and because Google has made poor design choices about handling links, you can go into the app settings to tell it to handle every YouTube URL. This should works when clicking a YouTube link from Sync. However, for links that you changed manually from Piped to YouTube, Chrome doesn’t provide a way to open in app. Firefox can do that, but if it’s not your default browser, this option requires you to change browser every time you want to see a video inside the app.

The best option, is to use “Open Link With…” which provide an easy way to open apps from your browser. It’s as simple as sharing the website to “Open Link With…” and select your app eg. YouTube/ReVanced/Vanced/etc. You can also set it as your browser which should do that automatically but I haven’t tested it so YMMV.

I hope this was useful!