LineageOS, Graphene, etc. all require AOSP at their core. AOSP contains the necessary binary blobs to activate hardware features in proprietary chips like modems, graphics controllers, etc., and also the communications infra for proprietary blobs on devices to talk to the OS in the case where the blobs have to be extracted from a proprietary ROM and ported over.

While those OS forks could continue to exist for some years, and probably will, they’ll be hitting an increasing uphill battle.

Problems like:

• Newer hardware will not have support.
• Existing hardware may lose support when the OS<->RIL<->Modem have updates in some way that are out of sync with the old code.
• More pieces of Android going forward will be closed-source, and it will become harder to maintain open versions of them without continual reverse-engineering of closed-source software, and the lawsuits to come.

The third-party OSes (all of them) have always been dependent on current AOSP existing. Without it, they will be missing the OS core to keep things going.

Isn’t Lineage reliant upon AOSP existing, though? I imagine it’ll be tough surviving for them once all the restrictions Google’s been announcing are put in place…