The blobs are required by hardware OEMs, not by google themselves. You'd have the exact same issue when trying to run pmOS on the same hardware; it actually crops up throughout the embedded ecosystem. Pinephone and Librem 5 are quite exceptional wrt. minimizing the amounts of hardware-specific blobs that they require.
Yeah indeed I should have specified that the whole "mainline linux compatible" is mostly because the Pinephone and the Librem don't use Qualcomm (or worse Mediatek) SoCs.
With a bit of work a lot of this can be improved, Android likes to have userspace drivers while a bunch of that stuff is also already in the kernel, so postmarketOS uses kernel drivers.
