Best phone (smartphone) for custom ROM?

I am sorry for intruding, but what does this above-quoted phrase mean? That the phone has separate blocks of dedicated ROMs of say, 10GB size each, the total ROM being around say, 200GB?

Whom is the question intended for? The OP?

I am not sure if it is just me, but the flow of conversation doesn’t really sink in, other than that a particular smartphone is the best suited for Open Source Android and apps; like LineageOS, GrapheneOS, DivestOS, etc., accompanied with F-Droid apps.

Yes, I am aware that I am a little lesser-gifted on the cognitive front, but then the Social Contract is supposed to appeal to you to clarify the flow of some bits of discussion.

Please, could anyone help here?!