I have a netbook with GMA 500, it has closed source driver for XOrg 1.9 (ten years old) and corresponding kernel [1]. I bought it because Intel graphic cards had open source drivers, not this one. Later I thought as you - someone would hack it, yes, kind of - there is a version without hardware acceleration. Eventually I was living with outdated XOrg server and patching driver to support updated kernel [2]. That I think is about as good as LineageOS - much better start than iPhone.
Hacking out of necessity is a bad idea. If not PinePhone I would definitely check open source drivers support in Replicant [3]. iPhone is too far away (and its users like iOS).