I bought a Samsung Galaxy S5 to use as a glorified DAP and pdf/ebook reader (because I had one back in the day and remember liking it), but the firmware is so old that I can't even sign into the google play store to download the necessary apps, nor will the phone allow me to install loose apks despite turning the option on in the settings.

I've read a little about custom recoveries and roms, but the problem is that the tutorials I found on youtube were all made by indians being incredibly vague and linking sketchy websites in the description.

So I was wondering if there are any retard-proof instructions on how to get this old ass phone working as a digital audio player and ebook reader.