So, I really wanted to have a solution for listening to Tidal on my iPhone through the Hugo2 with EQ. It'd be nice if Tidal would implement EQ or if Apple would add the ability to use audio units on iOS.
CapTune allows EQ for Tidal on mobile phones. The only problem is that it's UI is somewhat lacking. Below is what I created as a first pass for equalizing the i4. I used KMann's curves as a template, but there's no way to get enough nodes above 1k to do all that he did. The other problem is that the program gives you no way to know the magnitude of the changes you're making. I have no idea if the dips below are 3dB or 10db. For scale, the screenshot was taken on an iPhone 7+.
Something to watch out for: almost everytime I unplug my headphone and plug them back in, CapTune will revert to the 'Flat' eq setting.
Hopefully someone will find this useful.