I no longer recommend OnePlus
I often avoid talking about brands because no brand is perfect. Some in the Android community are also loyal to a brand no matter what they do, while I'm loyal to good products, so discussions often lead to heated arguments that go nowhere. I'm making an exception here because I've been recommending OnePlus for a while and I think they're no longer the best option if you want to use GCam.
To give you an idea of where I'm coming from, I can use all cameras and use full resolution (48MP in my case) with GCam (and other camera apps) on my Asus Zenfone 6 without root or any special GCam version.
GCam support for most OnePlus phones is "okay", but OnePlus is adding artificial limitations and breaking features via software updates, and there are no indications that they'll improve.
Until not long ago, the OnePlus 7/7T, 8/8T, and Nord series couldn't use all cameras without root. This by itself was already bad, but when a developer found a way of accessing all cameras, OnePlus decided to block his method with the Android 11 update.
Android 11 users now have to use a specific app package name. This means that users have less choice, can only use 1 version if they want to use the extra cameras and end up losing some GCam features not available with this package name. It also forces modders to do extra work to support OnePlus devices and not everyone is inclined to do so.
I've heard a few reasons for this "block". From OnePlus being worried about possible security issues, to them wanting people to use their own app instead, and even because they didn't like the negative feedback from users when they found out that the sensors used on the wide/macro/telephoto cameras are far worse and cheaper than the main sensor.
I don't know what's the true reason, but from a user point of view, this is not acceptable. I'm not aware of any other "dev friendly" brand being so aggressive when it comes to the auxiliary cameras.
Full sensor resolution:
This is not exclusive to OnePlus - Xiaomi, Samsung, Realme, etc, do the same at least on some of their phones - but on top of the auxiliary cameras limitation, OnePlus also blocks access to the full sensor resolution. Your phone might have a 48MP, but you can only use 12MP with 3rd party cameras.
It's another artificial limitation. Using the full resolution (48MP, in this case) instead of the binned resolution (12MP) doesn't always make sense (especially in low light), but it can improve details a lot when there's enough light (eg: outdoors).
Two samples from my Zenfone 6, which has the same Sony IMX586 sensor as the 7/7T, 8/8T, and Nord series. Look at the text, for example. 12MP on the left, 48MP on the right:
I can't think of any good reason to stop 3rd party apps from using the full resolution when the sensor supports it and the stock camera can use it.
Reasons behind this post:
I have been recommending OnePlus to people for a while, however I don't agree with what they're now doing when it comes to 3rd party camera apps. I don't want people to buy something based on my previous recommendation just to find out things are not as good as I said they were. This is the main reason.
The second reason comes down to what I expect from certain brands. For example, I might expect good custom ROM support from a "development friendly" brand, but not from others. Some people buy OnePlus and not a Samsung for this reason.
While it's true that OnePlus strategy changed since the OnePlus One days, they still advertise on XDA, send phones to developers, etc. They don't do this because they are nice, but because they want us to buy their phones (and I'm fine with that). My problem is when they present themselves as (still) being a development friendly brand and then act like a Samsung or Huawei.
On one hand, they send phones to GCam modders and some of their staff, on their own forums, suggest GCam to users unhappy with the stock camera performance. On the other, new phones come out with limitations and when someone finds a way to go around said limitations, software updates quickly break things again. There's no internal communication at OnePlus or are just trying to gaslighting us all?
It's not my intention to tell you what to buy. We all have different preferences, budgets, and brands we want to avoid, so doing that would be a hard task, but be aware that GCam and OnePlus are no longer the best match and that there are cheaper phones out there with less limitations.