I don't know how this works in country, but our justice allows us to unlock bootloader, root, install own software and so on. If phone damages somehow, company you bought phone from must prove that your software, your modification or your new non original battery caused that issue (which is bootloop). I I think that bootloop issue is not related to root, installing own ROM or using non-original battery.Followup to my above post-
I called LG's support line, US branch. I only had to tell them the phone wasn't booting and they immediately mentioned the word bootloop by assumption (guess they are getting extremely common) and agreed to help even with my no warranty SEA version. Though she said they'd be sending me a new US carrier G4 instead of repairing my H815 SEA version. They're not charging me for anything apparently.
Now I still might end up hitting a snag. The original LG battery failed and expanded enough to actually pop off the back cover. Given the fire hazard involved, I disposed of it immediately. Official LG batteries were $40 at the time, too pricey compared to higher quality third party ones. Got a TQTHL instead and it works great. But i'm concerned that this may impact my ability to get service. The LG rep said she didn't know how the service center would handle the situation, though suggested I try sending it in anyways with the replacement. So i'm including the replacement battery and a note explaining it. Hopefully they will be accommodating, we'll see...
I hope that lawsuit will change they their mind and they will start repairing all devices even with expired warranty or they will offer to all LG G4 owners money back or new, non affected phone. (Btw. all new SN mobos - even manufactured in 2017 aren't bootloop resistant). They still changed nothing.