I can only estimate zero, given that my M300 shows that 32 of 32gb of internal memory is already being used by my 16 apps, including the 6-or-so pre-installed ones. My 280-or-so gb of mostly-FLAC music files are all loaded on my installed 512gb microSD card. I can understand you only knowing or wanting internal storage use as an iphone user, but/so this device probably is not for you and I don't know of DAPs that have more than 32gb, especially at this price, and this is much more internal memory than the HiBy R3 and R5 devices I've owned. BTW, I do use Amazon Music on the M300, but I don't tend to download much music at all. In any event, I do require and use SD-card storage on all my portable devices and would download there as necessary -unless it was not allowedI guess for me the tidal issue or non issue is crucial. It is all I will use the DAP with. I will download the albums from tidal as I do to my iPhone.
How much internal storage is left on the M300 after all of the apps and google play are on the device , an approximate figure would be helpful
--- P.S., Newcastle is one of my favorite two beers and I'm always negotiating for sufficient storage space.