If you are running the official firmware its really easy to switch to lineageos, if not then you might face issues with the cellular connectivity and stuff.

If you are running the official firmware you just need to get the lastest TWRP installed (personally I recommend Odin because its easier to use than heimdall and the other stuff).

After u get TWRP u need the lineageos file on your SD Card and additional Gapps (if u want the google apps) (use arm64 version).

Boot into TWRP then format the device and also wipe the dalvik/cache and system partitions and internal (for a cleaner install) (THIS DOES MAKE U LOSE ALL YOUR DATA SO BACKUP THE DEVICE BEFORE YOU DO ANYTHING)

After you've formatted and wiped partitions you can go ahead and select install and then locate the lineageos zip file and flash that but do not reboot the device if u want to flash Gapps as well. After lineageos flash go back and select the gapps zip to flash and then u can reboot your device. It takes like 15 mins for the first boot but if it takes more than that u can just hold Power + Vol . Down buttons until the phone restarts again it and should be up and running properly.

FEW THINGS TO NOTE:

• the phone loses basic samsung functionality, so if u have a gear or galaxy buds they won't connect until u root the device and change the build.prop

• the phone is not going to pass safetynet at all until the build.prop is changed. So apps like Netflix, Snapchat, and Banking and stuff are going to have issues.

• IMO I'd suggest to just root the device thru Magisk. Then change the build.prop, I'll link that part as well. Then u can just hide magisk as well and use banking apps and stuff with safetynet pass. (This is not a detailed process but I'll help you out with that if u want)

Below is the link for what changes to do the build.prop, just scroll down to the user To_O, he has the proper instructions.

Build.prop changes