sudo apt-get install heimdall-flash
# Boot phone into download mode: --> Hold Home, Volume Down, and Power
heimdall flash --RECOVERY twrp-3.0.2-2-i9300.img --no-reboot
# Manually reboot into recovery: --> Hold Home, Volume Up, and Power
# wipe Dalvik Cache, Cache PArtition and System Partition - !WARNING: DO NOT WIPE DATA PARTITION!
# install LineageOS experimental version (zip file) via recovery
# reboot into regular OS, wait until data conversion has completed
# Manually reboot into recovery: --> Hold Home, Volume Up, and Power
# install LineageOS daily build version (zip file) via recovery
# install Open GApps (e.g. nano version) (zip file) via recovery
# wipe Dalvik Cache
# reboot into regular OS, wait until data conversion has completed
# go to "System Settings" -> "Apps" and delete Data and Cache of "Google Play Store" and "Google Play Services"
# go to "System Settings" -> "Storage" and clean Cache data