ISR code must be in ICACHE_RAM - the check was commited in ab125162bf

[dok-net]

#5995 hasn't actually merged any PR - the minimum to get actual code working is in this PR.
Caveat: I don't know how to check if ICACHE_RAM_ATTR has the desired effect on lambda expressions, if it does not, there will still be an adverse performance (no real-time behavior!) impact over the standard Arduino attachInterrupt() usage.
Q: why not implement void attachInterruptArg(uint8_t pin, void ()(void), void * arg, int mode) like the ESP32 has already?

[d-a-v]

why not implement void attachInterruptArg(uint8_t pin, void ()(void), void * arg, int mode) like the ESP32 has already?

It is the same

typedef void (*voidFuncPtr)(void);
extern void ICACHE_RAM_ATTR __attachInterruptArg(uint8_t pin, voidFuncPtr userFunc, void *arg, int mode) {

[d-a-v]

I don't know how to check if ICACHE_RAM_ATTR has the desired effect on lambda expressions

I used that code: #5780 (comment)