Used Devices: Security and Finding Unlockable Bootloader

internic

I'm currently using a Pixel 6, which will unfortunately cease being supported a while before the new Motorola GrapheneOS phones come on the market. Since I've been happily using a Pixel 6, I clearly don't need the latest and greatest phone, so I was wondering about buying a used Pixel 8 or 9 (to save some money and reduce waste), but I have two questions:

Is buying a used device generally considered a secure option? I would obviously be flashing GrapheneOS on it, so I'm assuming that would address most potential threats, but I don't know a ton about mobile device security, so is there some plausible thread I'm missing there?
To do this you obviously need to get a device with an unlockable bootloader. But most buyers are more concerned with finding a phone that is carrier unlocked (a distinct thing), so how can I actually be certain that the phone I'd be buying would have an unlockable bootloader? Are there some marketplaces where this is easier to determine?

de0u

internic I have had good luck with buying used devices listed as "factory unlocked" on eBay, from high-volume sellers with good return policies. There are professionals out there, and professionals have good return policies and high volumes and use terminology carefully.

I would recommend using Auditor as soon as installation completes. One subtle reason for this is that some odd devices (e.g., demo units from stores) will appear to install ok but will fail Auditor. If such a device came from a professional, it should be easy to return it.

internic

I think I've also seen people use the phrase "OEM unlocked" for this.

internic

So far looking at Swappa I don't find any older Pixels listed as "OEM unlocked" or "factory unlocked", so I may have to cast the net wider.

de0u

internic I think that searching the forum for "Swappa" may turn up reports on how their return process works out in practice.

The-Man

There are good people out there reselling devices, you just have to put the time and effort in, that's all
My go to reseller has been in the business over 25 years, consistently evaluates condition of devices accurately and takes back devices without question.
Do your homework people and when you find one, keep them to yourselves.