I bought a back adhesive, a screen and a battery for my OnePlus8T.
First of, I have got to say I have been very well served by customer support, granted it was to buy more from them. But anyway, very friendly!
I was afraid the screen wouldn't be great as there isn't much garantee about the quality and inherent specification (120Hz, sRGB, display P3). But while I can't assure all is there as I don't have specific tools to verify it, to my naked eye, all seems fine! The fingerprint scanner seems to take longer and as soon as there is a tiny touch water doesn't work at all (which wasn't the case before), but it works, which is fine. The touch screen is less sensitive than before too, i can't use gloves anymore.
The battery lasts at least as long as how the original one was at the beginning.
Everything wasn't perfect, and that's why I gave it 4 stars. The battery was 1mm too long and I had a hard time putting the rigid cable in its slot. I had to push the battery a lot to fit it in. 1mm seems like alright, but it could very well haven't been.
The screen has sort of a coating on it that is spread on 3 vertical bands 1cm wide and one horizontal one. These bands aren't visible when the screen is on, but while off it can be seen under certain reflection angles (many). I tried to rub it with alcohol, but couldn't take it away. I suppose it's a process during manufacturing that made it. Doesn't seem to have consequences, but weird.
All in all, my phone works again, so thank you!