I use a lot of mcu with Arduino IDE. In terms of compatibility of hardware add-ons, I don't use v2.x.x, but I often try to see where the process has changed.
_delay_ms(x), delay_ms(х), delay(х) - each is in place and lights up normally in v1.8.9, but I see no response in v2.1.0. This is useful! It's missing on v2.1.0.
And does it have a function/doesn't it in program, is there a void ... in front, it lights up red. Why?
(sorry for my english, it's with a g. translator)