FiXemanHi @FiXeman. Yes, I've enjoyed various IEM with the M5, including my beloved FLC8S and Oriveti Primacy triple hybrids, Campfire Audio Orion and Unique Melody Miracle and Maestro BA IEM, and MEE P1, RHA T20, and Shozy Zero dynamic IEM.
As mentioned in a post above, the Output Impedance rating reported by Shanling is less than one ohm so you're not going to see detrimental impact on BA or hybrid IEM. This means it's going to be about synergy rather than technical limitations.
Hopefully that was helpful. If not, please ask follow-up questions as needed.