Re: Wot, no Sammies?
From the Lineage OS supported devices list, it doesn't seem like Samsung is terrible. Of every manufacturer on the list, Samsung has the highest number of supported devices (71 versus 33 for the next highest, LG). However, I note that Samsung's list has quite a few old devices and that some of their devices are listed many times for carrier-specific variants. I think it's a constantly-moving target in that a manufacturer can either be magnanimous with bootloader access or make mistakes that make it easy with one model and then turn around and change their tune quickly, similar to how Huawei locked its bootloaders a couple years back and have fallen of the list of good devices for replacement firmware.
The other side of that coin is that a device can have a completely open software stack and still not get much attention. Only if the phone is owned by enough people will the work get done. At one point, I had found a device where basically everything was open (even most of the hardware, strangely), but it was not found by anyone else because it didn't even have a brand name (I still don't know who made it), it was intended as a very cheap device with poor specs, and by the time the previous owner gave it to me for erasure and I figured out how open it was it was three years old.