See i.MX8M reference manual, page 776 :
"The ETM can be accessed either via JTAG port and/or by direct software code". and on i.MX8M EVK board, JTAG port has been supported.
About emulator, you can use Realview ICE and DS5 .
Actually, You don't need emulator if you design a product based on i.MX8M. We provide serials tools for customers, such as DDR stress tool , uuu tool for downloading image etc. Very few customers uses emulator on i.MX8 to trace A53 core.
Have a nice day!