Stable Android 11 update is available from many custom ROMs such as LineageOS 18, Pixel Experience 11, RevengeOS 4.0, StatiXOS 4.0 etc. for various devices.
Custom ROMs usually do not have GApps or Google proprietary apps built-in. So, developers provide Google Apps separately in recovery flashable zip format.
This page provides Android 11 FlameGApps download packages.
Latest update: 18th September 2020