>>663919041. install TWRP using heimdall
2. boot into TWRP, and do a whole-phone backup
3. install oandbackup, backup your app data and settings
4. install lineageos, addonsu, and gapps (if you want gapps, which judging from your response, you do)
5. install oandbackup, restore app data and settings
play with it for a bit, if you like it, keep it, if not, boot back into TWRP and restore your backup, it'll be like you didn't touch anything
it's not some riced up hack-job. it's really quite vanilla, really, it's more vanilla android than the stock samsung rom
and importantly, it's maintained, with up to date security patches and features
don't be put off by nightlies either, i've been using them on this phone for 4 years without issues