[RESOLVED] For all having compile error: LTO version 4.1 used 6.0 expected...

If you want a temporary way around this problem, here's what I did. NOTE: THIS IS NOT A FIX, JUST A TEMPORARY WAY AROUND THE PROBLEM SO YOU CAN TEST CODE...

Pause your plugin
Download and Install Arduino IDE v1.8.9 on your HD (the last, older version available on webpage)
Don't use the online IDE
Restart the plugin

Worked for me. I have local copies of my projects and coding.

WARNING: if you have to uninstall an Arduino IDE from your hard drive, I didn't have to uninstall and I'm not sure if your project and code files will be saved or protected. Have backups ready just incase. You've been warned. Don't blame me if you lose files.

According to the team it was fixed.
Thanks for your report.