Hello,

I've made necessary changes to MySensors 2.4.0-alpha in order to work on Odroid-N2 SBC running Ubuntu 21.04 with 5.13.0 kernel
Library would have worked if every reference to pin number was at least uint16_t (not uint8_t, like it is). That's because Odroid-N2 have >2^8 pin numbering, and GPIO ranges in 460-490 decimal.

I've made my fork@github and pushed odroid-n2 required changes version.
Using polling (non-IRQ) mysgw drains 1.0% cpu time.
Still waiting for interrupt issues to resolve with HK team - hopefully soon.

Github repo @ https://github.com/Gobol/MySensors

Ok.
Some progress.
I've ATtiny 3227, so tested on it, with RFM69, works in IRQ mode ok.

How to use:

• download library from github & replace in-place in arduino user lib folder
• use SpenceKonde megaTinyCore for newest ATtiny support
• required define (non-standard) goes into main sketch file (.ino) before <include "MySensors.h> :

#define MY_RFM69_IRQ_PIN PIN_PA5
#ifdef MY_RFM69_IRQ_PIN
	#define MY_RFM69_IRQ_PORT_vect        PORTA_PORT_vect
#endif

https://github.com/Gobol/MySensors