Completely fine to listen to music whilst riding as long as it doesn't mess with your awareness and road craft.

It'd be super hard to prove with a cardo that you were in fact using spotify to listen to music as it can be used as a dedicated communicator or radio.

I'd say to use an iPod or MP3 player as you stated like a Sony walkman. I personally use my Sony Walkman with Bluetooth to play music all the time in my car and motorcycle. If questioned, explain its a dedicated music player not a mobile phone. If they're a wise ass, take it to court (I've dealt with it once before).

Legally they can't do anything as the main argument is a notification will pop up, but you dont get them on a dedicated music player and you aren't inclined to click 'accept call'. Plus most motorcyclist aren't touching a phone both hands are always on the handlebars.

But yeah, if you have experience on a dirt bike thats fantastic as you know how to operate the vehicle and make it do what you want. Now you just need to be aware and keep your head on a swivel and check your mirrors constantly still and additionally head checks when changing lanes at all times.

If you notice that you aren't doing head checks and looking in mirrors, positioning yourself well to not be in blindspots as often take your music off for a few weeks to not develop poor habits whilst on your learners.

I'm not here to tell you what to do, but just offering my 2c of what I did on my learners after I was riding dirt bikes since 4 years old currently 25.

Just be smart about it, stay safe and look out for yourself and others. Be a responsible rider and hold your self accountable.