Ask HN: CS, Maths or some other degree for an experienced dev?

// this is a repost, for some reason I couldn't submit it properly yesterday with description

Hi. I'm a self taught dev doing web development for 4 years now. I switched few shops and eventually found a company with excellent engineering culture. I love everything about my job now, but I feel like I'm missing out on some more exciting areas in CS.

Hence I'm pretty determined to get a degree (it's free, I'm in Europe). I've been settled on CS, but just today I've read here on HN that it's not that good of a choice for people who can already code. Mathematics has been recommended and also Physics. This has been a interesting idea to think about, but I'm having troubles deciding and love to hear your opinions on the matter.

I like maths, but I'm not a nerd for it. I understand that CS is mostly maths, I'm okay with that and therefore I'm also open to alternatives. I don't exactly know what area I'm interested in - that's why I want to get a degree in the first place, to find out which would interest me.

What I'm looking to get out of it is specialised knowledge that would allow me to work in that specific field or start my own company. I'm also not sure if that would mean that I'd need a PhD. I'm open to it as I have a strong passion for science/tech.

Any insight will be much appreciated. Thanks!