Limit them producing PCIe cards to low volume reference models and require their software to be open source to break that aspect of the lock-in, that's the two big things. As alternative to the latter, require them to have actual platform docs, right now they're not only providing the only compiler for their cards which is deliberately incompatible with everything else they're also making sure that noone else can get performance out of NVidia cards without excessive reverse-engineering, some things are even locked down hard via firmware signing. Splitting AI off from GPU would be a bonus.