Now we are doing pcb design with iMX8MMini and I have got same questions:
1. I have got the same problems with conversion Allegro layout files into Altium. The Allegro layout files from the website in 8MMINILPD4-EVK-DESIGNFILES.zip cannot be converted within Altium.
Could you send me correct Allegro layout files?
2. In the datasheet of iMX8MMini I havent found footprint for pcb. What footprint do you advise to use for FCPBGA-486?
NXP Web contains officially provided and supported i.MX8Mm design files.
In addition I've sent You .alg files via e-mail. Hope it helps.