Android 6 marshmallow firmware for the Samsung Galaxy Ace 4 is here and it allows you to enjoy the latest android features. Gapps are not included in the ROM. The ROM is based on latest cyanogen mod 12 firmware that is basically android 6 marshamallow but since it is CM12, you will not find Samsung touch wiz user interface or any bloatware that came preinstalled in your Galaxy ace 4 firmware.
The developer behind this Android 6 marshmallow ROM for Galaxy Ace 4 claims that it is near bugless and pretty much everything is working just fine. He does points out that FM radio is removed from the firmware. Flashing the ROM is easy – download the latest nightly built from the link given below and place it on the micro SD card. Boot into galaxy ace 4 custom recovery and flash it from there.