Yeah, the usual problem is that people who don't know better will call the MegaRAID cards "IR mode", which it isn't. IR mode will fall under the same mpr/mps driver but be a few percent slower. If it's showing up as mpr/mps, it's usable, assuming the firmware rev is correct. If it's showing up as mfi, it's not. End of story.
I should point out that LSI 3Gbps mpt based cards still work fine, with the caveat that they're limited to 2.2TB HDD's (32 bit LBA limit). "Very old" is all relative in this biz.