Most of you probably depend on this mod, like myself.
Officially xda is no longer its home, so you’ll need to look elsewhere.
Basically you’ve got a couple options; google it or ask someone who knows where to look already.
I personally think the latter option is better.
Looking around on google or bing isn’t going to find you the best options – they’ve intentionally buried those results.
If you’d rather not waste your time googling, then go with the other option.
Simply read between the lines.
Most of the time, the answer is right in front of you.
EDIT: As mentioned by another user, there's no guarantee that the version(s) of Spotify you find on other sites will work. All I'm saying is that if we are able to get a coder to take up this project again, we need a different site *cough cough* that is more friendly about these types of mods. Until that happens, I would simply recommend staying on an older version of Spotify that works well. Personally, I'm still using a pre-popup version, and it works wonderfully still.
EDIT 2: As with everything done on the internet, it is imperative that one uses common sense and does some solid due diligence before clicking links, downloading files, installing files, or even visiting websites. Things like Adblockers have their place in many instances, as do other similar tools, however caution and knowledge are still your top defenses when you're on the web. Read carefully, ask questions, and make sure you know what you're doing before you do it.