> near-stock
I have now got a Nokia 7+ which has "Android One" (very close to AOSP) and it has been a great piece of hardware which gets updates. I think HMD Global dealt brilliantly with the security issue that affected some phones.
I agree about Moto though, in the past I have bought four Moto phones (G1, G3, G3, G4 - two were presents) and I had zero hardware faults (although they all stopped getting updates far earlier than I like). A G3 and G4 are still in daily use. One G3 broke a screen (teenager), and I can't remember who I gave the G1 to when I upgraded.
Multiple previous experiences with Nexus line have left me disappointed, and so far the Pixel's have been too expensive for me to want to learn the same mistakes again.
Hopefully the 3a will be better!
I also used to use your rule: if it was bootlocked then I wouldn't buy it.
However that rule has never helped me use CyanogenMod/LineageOS etc because:
Galaxy Nexus: Screen burn in (OLED blue) and obsoleted OMAP processor so didn't update, then gave to friend's kid.
Nexus 10: Kept at factory 5.1.1 for testing at work. Then tried updating this year but flash partition was too small to install gApps.
Nexus 7: Gave to family member who updated it, but it then died from slow flash hardware issue.
Nexus 5: broken frame (leading to common hardware faults) - no point updating.
Nexus 5X: Never used much - can't use as daily driver due to perceived risk of boot looping - so it is sitting in drawer at work.
Moto G1: Gave away a long time ago
Moto G3: Broken by teenager
Moto G3: Gave to friend (still in use - but can't unlock G3 any more)
Moto G4: Was a present to a friend (still in use by them, they not likely to update or want update)
Edit: Some of the devices were bought cheaply (second hand) and more than one device was paid for by work as we always need recent Android devices to test App releases on.
My nokia 3 get's updates, shame they won't install. Then again the android one updates have been breaking enough random stuff that it might be a blessing.
They also come with almost non existent Android upgrades.
EDIT: Wow, apparently they are still advertising and selling this model for which they haven't released a security update in almost a year!
Except that they seem to have wholeheartedly jumped on the "I need a phone so big it won't fit in my hand" bandwagon. As far as I could tell last I checked, they don't sell anything in this size range.
I unlocked the bootloader but then never installed a ROM because the stock one is close enough to vanilla Android to keep me happy.