LG Gram user here with Debian as a daily driver. Can confirm, maybe not 15h, but I don't think about charging. Plus, it's super stable, not a single crash or hang-up over years. It just works. I hope LG will keep this up and not mess up next iterations of the hardware.

I had an LG gram before the battery in it gave out and now it won't boot with the battery plugged in. The battery life was amazing, it always slept properly, etc.

Now I have a Framework. It randomly reboots when I close the lid, the battery life is terrible, etc. I live with it since I like the idea of a repairable laptop.