I have lineage OS 14.1 currently. I want to update to Lineage OS 15. Should I clean flash Lineage OS 15 or update it via updater app from setting. Which way is better? Can I use gapps from 14.1 after updating to 15.1?
Backup your data and Clean Install, you will need to flash gapps for 15.1 also. Clean install cleans all the junk and the phone runs smoothly. Unless you want to keep the data and settings, then you can update it.