I’m not sure if it’s possible simply to create a second apple account, and sign out on your primary device, and sign in with the secondary apple account?
That is quite possible. The Apple ID you use to view and pay for apps, music, books, etc. can be different than the ID your phone is registered under and used for messages, FaceTime, iCloud, etc.
Go to Media & Purchases under iPhone settings > <your name>. Log out and enter the Apple ID you would like. Note however, any content you have downloaded through the Music app with your Apple Music subscription or even the playlists will be deleted once you do that and you can not reach the Apple Music service subscribed under the previous Apple ID. They will come back only when you re-enter the previous Apple ID, but you will have to probably re-download anything deleted if that is what you need.
For example, I have Apple IDs from two different countries. Occasionally, there is an app not available in the App Store associated with the Apple ID I have active most of the time on my iPhone. I log out of that ID under Media & Purchases, log in with the other one, download the app I need from the App Store, and then go back to the previous Apple ID.
The app I downloaded using the other Apple ID remains unaffected by the change including any subscriptions or in-app purchases. However, you need to log in once in a while with the other Apple ID and update those apps if necessary.
