What lcd buyback website should I trust?

There's next to no demand for S6 parts today since so few repair them due to the cost and age of the phone, as well as the SW being so dated. I had 2 (an S6 and an Edge+). Frankly, I let both of mine go because both had a fatal issue: The Edge+ battery failed (again! And no, there are no good ones left), and the standard S6 had a bad MicroUSB port. These days, I have a "rule" that I will not repair a phone that is too old to have a USB-C on the Android side. They are too risky and prone to being next to be blocked for future activations as the carriers free up network spectrum to refarm it for things like better 4G bands and 5G by the big 3 in the US. For that reason alone, you will find it hard to resell your old screen :(.

And yes, this is coming from someone who took a bootlooping Pixel 3 XL and moved the working board to the frame for a burner device. Believe me: I don't condemn an entire phone generation for a port issue like this for no reason; it took seeing many of them get hit by the US network sunsetting 3G and not carrying them forward after the sunset to get there. MicroUSB is a red flag today!

To give some needed contrast to put it into perspective: The Pixel 3 in 2018 is about the same time MicroUSB went away outside of really cheap phones for a very long time). This is the oldest Pixel still supported by the carriers, the Pixel 1 and 2 were cut off with the US 3G shutdown. This is the LAST Pixel that survived the big US/CAN 3G sunsettings.

I wish I had better news, but in the US/CAN, anything older than ~2018 is at a point where the carriers will activation block the devices at the network level for new customers./device swaps (aka swap it, and the phone can never be used again) This also affects the MVNOs because if the main network refuses it, then the odds an MVNO can utilize these condemned phones are low. The S6 is well past that point, to the point where I took the batteries out, drilled through the flash memory, and then sent them out to recycling. The only phones that survived the US 3G shutdown bloodbath with years of age on them were iPhones -- specifically the six and up.

In contrast, the same generation of Android phones got decimated due to the inconsistencies of things like VoLTE, especially grey market phones purchased years prior, where AT&T refused to allow them on the VoLTE whitelist just because they're grey market devices. There are just too many wildcards with old Android phones before 2018 to know, but enough to know they're likely next to get cut. In other words: that $100 or so you spent swapping your S6 screen will be in vain within a few months if you're unlucky, or a year or so if you won the lottery and got one that makes it for the next wave of blocked devices. If someone asked me to fix one, I'd refuse the job and tell them to buy a new phone.

Yes, repair is good. On the other hand, there's a point where you just let the device go. It's time to let these old Android phones retire in dignity rather than trying to keep phones that are bordering on at risk due to their age.