Ok, version V1.1.0 of the I2C_DMAC library is ready and available on Github: GitHub - MartinL1/I2C_DMAC: Arduino Zero (SAMD21/SAMD51) based non-blocking I2C library using the DMAC..
The new library in additon to the Arduino Zero, now supports the Arduino MKR series (untested) and the SAMD51 using Adafruit's Metro/Feather M4 core code (tested).
It also supports multiple I2C instances. An example sketch "MPU6050_Gyroscope_V2.ino" that reads the raw gyroscope data from two gyroscopes on separate I2C ports, is also included.