That's a wishful thinking. Majority of Android drivers are userspace blobs. Linux kernel development process is completely irrelevant for them.
Device vendors don't update already sold devices because they don't care (and because average consumer also does not care).
You should consider why the hardware vendors are in the critical path for OS updates in the first place. Dell doesn't get to decide whether you can apply Windows updates.
They more or less intend to supply the hardware only. This avoids the pretence of vendor updates entirely, by both the company (Pine64) and the ARM licensee (Allwinner).
The software stack is up to you, with mainline Linux support courtesy of the A64  powering a number of 'RPi-killer' boards. Device updates will be supplied by the likes of Ubuntu Touch, LineageOS, postMarketOS et alia mobile distributions.
Maybe. Except that for me (and I know I'm not alone) the second most important part of my pocket computer after web searching is the camera, and they're unlikely to have anything great in there.
Hah. The repeat GPL violator?
thereby we get the constant tension between google and hardware makers that want to keep their jewels secret, and the linux/foss community that wants to keep their freedom to install their (open) software on any device... by keeping the drivers in with the kernel, linux can foster that end, but it causes no end of frustration to google et al...
i think that’s probably the reason we get fuchsia: google can be open source, and with the hw makers, keep the proprietary parts proprietary... the result being, we have open kernel and os bits but no guarantee (or much hope at least) we could ever run it on our devices...
i think that’s the biggest cultural divide: freedom to change and replace the software vs freedom to look at the code (and maybe run it in an emulator...