Hello,
I have a headless pi0w sitting and a cheap usb sound card and I would like to control Spotify from my phone.
I’ve tested the dac and it works but I find it hard to start open spotify website from the terminal and see it in my devices on my phone. Even with a screen I think that Spotify checked UA to not allow you do this and people used UA changers
Is there any simple way to achieve it?
A more simple approach would be to use a Bluetooth receiver but hey…
I looked over the internet but most tutorials are about some clients (included in dietpi-software) that require premium.
btw also been interested in the solution to this problem. notify me if someone will help you, thanks in advance 
UPD
I found a solution to this problem on one site and I was surprised that the article was written on 10.04 - that is, on my birthday. I decided to learn more about this and came across this article https://www.sunsigns.org/april-10-birthday-zodiac-aries-cheerful/
I learned a lot of interesting things about my zodiac sign. I advise you to read!
Hmm there are command-line tools like ncspot, but I’ve no good idea how to control from mobile phone.
EDIT: Ah dammit, it seems to require a premium account as well, somehow all librespot based clients I know… I guess it’s the API itself which cannot be used without premium account and with a free account one would need to emulate a browser access, like you mentioned with browser user agent and probably other things. Interesting that I cannot find any projects which try to achieve this. Probably Spotify itself is active on fighting against such approaches so that one is forced to really visit the website, see the ads, be tracked etc, the common price for services without payment 
.
Kodi and Mopidy, which can be controlled via web interface, have Spotify plugins. But especially Kodi comes with the GUI overhead of course and I’m not sure whether those work without premium account. EDIT: Very likely they require a premium account as well.