So my first smartphone was the galaxy s3 and i loved everything about it (except the battery life) but when it took a shit i had to get an iphone because it was free and im poor. Today my "Xiaomi Redmi Note 4X" arrived and im looking to get back to the kinda linuxy feel the s3 had (think it was jellybean or kitkat) can anyone suggest up to date OS options?
Not familiar with that phone. I run LineageOS on my one plus 3 and its flawless.
Have you checked XDA for your device support?
As @SudoSaibot suggests, check XDA to see whats even available for your phone. I typically stick with rooted stock roms these days but I'm on a nexus 6p so the difference between rooted stock and custom rom is not much. If I had to go to custom I would probably go for OMNI or PureNexus. I havent tried LineageOS yet but seeing as its a fork of CyanogenMod, which was what I used previously on my older nexus devices, it's probably good. The other thing LineageOS probably has going for it is large phone base it can be flashed to so there is that.
xda website has handy stuff for bootloader/unlocking the phone and whatnot thanks for that, will belooking into suggest operating systems in my spare time. for now i will just be enjoying having FLAC and VLC again for my music.
Lineage's site shows no support for that phone. Not sure what other options are there, the XDA forum will be your best bet.
https://download.lineageos.org/
It's a bit late for that advice now, but if you want to go the custom ROM route always check out what's available for a phone BEFORE you buy it.
(I found out the hard way too last year, still running my Galaxy J3 on the stock ROM because there's just nothing out there)