Google isn’t releasing the app for older smartwatches running on Wear OS 2. Which means your only option for getting the app on your Fossil Gen 5 or similar devices, is to sideload it. Except, this won’t do you any good. Once you sideload the app, it still won’t work. So you’ll have to use something else instead. Spotify for example.
Sideloading YouTube Music on older Wear OS devices requires API level 30
What this comes down to is that the app requires a minimum API level of 30 to function. In other words the software has to be based on Android 11. Wear OS 2 isn’t based on Android 11 though. It’s based on Android 9 and has an API level of 28. So sideloading the app only ends up giving you an error message. If you’re savvy enough to lower the API level to match Wear OS 2, you could get the app to install. But then you’ll just end up with another issue. Specifically not being able to login to your Google account to use the app. Since Google doesn’t appear to have any plans to release YouTube Music for smartwatches running on the older software, you’re out of luck if you were hoping to use it. This is mostly a shame for anyone that was heavily invested in Google Play Music. Now that Google has shut down that particular service, which did work with Wear OS 2, your only option for keeping all of your music was to transfer it something like YouTube Music. Unfortunately, that leaves anyone who did so without a way to use their older Wear OS smartwatches for music playback. Unless they switch to using Spotify or some other option. The good news for some TicWatch owners at least, is that Wear OS 3 will eventually come to a handful of those devices. So YouTube Music will be an option at that point.