I do the opposite, and buy a lot online. But every time one arrives I chuck the LP box/envelope/mailer (no idea what they are actually called!) in the basement and I now have a mountain of them. So if anyone sells online and wants to save a few quid buying new…whatever they are called, you are very welcome to them. There’s 132 of them, a few of which are bigger and can fit several LPs in. I’m in the town centre, off Summer Lane near the hospital.
I do a bit of both, but recycle all mine & I have a lot. Tells me I'm buying more than selling, I guess.
PS, try Andy in Vinyl Underground. He may be able to use them? Top bloke. Might give you a bit of credit on a purchase, if you have a lot.
Already been in to check, as I already give him any unwanted records, inner sleeves, vinyl outer sleeves, etc, but he only uses new boxes.