I have a passed down Iphone 5 which I literally only use it for listening to my Itunes music (outdoor exercise, during flight, etc), and watch a bit of youtube before I go to sleep (so i can plug and charge my other devices). Its battery pretty much dead now as the phone die at 70% battery.
My other devices are a Samsung S9 and an Ipad
So any suggestions on what is the cheapest/ worthy option that i can get that does the same job? An old Iphone? An alternative/ upgrade on current Ipad + wireless headset? Maybe replace the battery somewhere and prolong the current Iphone?
iTunes songs that you buy can be (mostly) downloaded & copied DRM-protection-free. (I say mostly because some older songs are protected.)
If you have enough free space on your Samsung S9, then you could copy over the iTunes songs and listen to them with some music player app. You can't play them using Google Play or iTunes, but there's other options.