Which firmware is recommended for ESP8266-01?

[caiossoliveira]

• [ X] This issue complies with the issue POLICY doc.
• [ X] I have read the documentation at readthedocs and the issue is not addressed there.
• [ X] I have tested that the issue is present in current master branch (aka latest git).
• [ X] I have searched the issue tracker for a similar issue.
• [ X] If there is a stack dump, I have decoded it.
• [ X] I have filled out all fields below.

Platform

• Hardware: [ESP-01]
• Core Version: [latest git hash or date]
• Development Env: [Arduino IDE]
• Operating System: [Windows|Ubuntu|MacOS]

Settings in IDE

• Module: [Generic ESP8266 Module]
• Flash Mode: [not sure]
• Flash Size: [4MB]
• Reset Method: [ck]
• Flash Frequency: [40Mhz]
• CPU Frequency: [80Mhz]
• Upload Using: [SERIAL]
• Upload Speed: [115200] (serial upload only)

Problem Description

Which version of firmware is recommended for ESP8266-01 to work in this environment? And what is the better way to upgrade?

[d-a-v]

git master with default values in menu, especially the 'sdk' entry:
it is currently called nonos-sdk 2.2.1+100 (testing) or NONOSDK22y with PIO or arduino-builder.

Best way to upgrade should be done after everything is uninstalled first.

(and this pull request #6484 if you are brave, but I guess it will soon be merged)