In my experience, Nvidia cards just don’t work well on Linux, because Nvidia typically hasn’t been friendly to Linux developers. I don’t have experience with the MX150, though, so maybe it is better.
In general, PureOS only includes 100% free software, and the nouveau drivers, which try to control Nvidia graphics cards, frequently cause problems. I do not think you will have a good time trying to use PureOS with Nvidia cards, and it is not part of Purism’s mission to provide support for proprietary drivers. Some devs may try to help anyway, but most of your help will probably end up coming from community members.
I would say use Debian instead, since it makes it easier to get the non-free drivers you might need.
i was on debian 10.1 earlier, dev’s were too sloppy to figure out this primitive graphics card!
So i shifted to other OS’s and finally to Pure OS, looks like Ubuntu will do just fine.