My earlier blog posts about FreeRTOS on the ATmega4809 (Arduino Nano Every) were for an older version of the FreeRTOS distribution, 10.3.0-9. The instructions for making the patches to the code don’t quite work for the more recent distributions like 10.5, so to use you will need to either install an older version or work through the changes. Also, there is a chance that sometime the 4809 will actually be supported in the distribution and these patches won’t be necessary.
Download the patched files for 10.5.0-0 from https://almy.us/files/RTOSPatches.zip You will still need to comment out the initVariant function in variants/nona4809/variant.c