Meson build system is now supported.
ESP8266_RTOS_SDK is once again supported, and tested. Building on Ubuntu 20.04 is now supported and tested.
Note: Python heatshrink is no longer installed for mkfrogfs per default. It is deprecated in favor of using zlib/deflate or gzip instead using miniz on ESP32. A workaround may be implemented for ESP8266_RTOS_SDK at a later date.
Full Changelog: v5.2.0...v5.3.0