[AT&T LG G4] br0adband:
Ok, so I happened upon an LG G4 H810 AT&T variant at a pawn shop a few weeks ago, they couldn't get it working because of the boot loop issue (person that pawned it probably did so knowing it was defective and had it working just long enough to demo it to get the cash). I took a look at it, great shape overall, no damage noted, plain old "ceramic" back cover, battery had a date of January 15 2016 on it so it's tough to say if the battery was just newer or the device itself since I couldn't get it to boot. Date code was 508 so obviously one of the well known defective models.

Long story short: got it for a pittance because they couldn't get anyone else to buy it, got it home, registered it at LG's website on my account, waited 2 days then chatted their support up and got them to accept it for RMA, shipped it out last week and it should be back tomorrow. I'm not sure if they repaired it or replaced it - the limited info I have says they "Swap Board (Main/RF)" so I'm guessing the entire motherboard was swapped for (hopefully) a newer one made this year that might not fail but probably will.

So, I had a question or two and I've done quite a bit of research the past few days and never found specific answers so at this point I'm just going to ask them and be done with it:

1) There's apparently no working root at all for the H810 that I've been able to find. I'm going to assume that the unit I'll be getting tomorrow or Tuesday will have been upgraded to Marshmallow unfortunately but that's just how it goes so there's no rolling back as I understand things. If there's a working root I'd be interested in knowing which one that happens to be. Also with no root there's probably no recovery either but I will keep researching to find out more as I'm able.

2) There's apparently no custom ROMs available because of the locked bootloader which will never get unlocked obviously as well. I've read that the PR (Puerto Rico) ROM could be installed on an H810 that was still running Lollipop with the v2 rollback but if this repaired board is Marshmallow that means it's been upgraded to v3 rollback and so that's dead in the water too.

3) I'm also going to assume that if the board has been replaced and hopefully is one made in 2016 (with a 6xx serial number) then it could last a while but there's no guarantee of it. I've seen people say the 6xx versions have not failed but then I find a post or two from someone that claims to know someone with a 6xx model and it failed at least once on them but I can't get any actual verification on it, that's just hearsay to me if there's no direct proof so all I can do is continue hoping it's a 6xx revision board and that it's not going to fail anytime soon.

This will be my second G4, had a Sprint variant last year and never had problems with it, sold it to a gent from Australia when he visited Las Vegas and as far as I know he's still using it, who knows.

If anyone can offer some info related to those questions I'd be grateful so thanks in advance if anyone can.

Have fun, always...

EDIT:

Seems that if I get very lucky and the replacement board comes with H81020n on it - the original Marshmallow build - there's a chance I can roll it back to H81010o using the TOT method from the other thread for it, that would at least get me root potential I suppose. Guess I'll find out tomorrow if the replacement arrives. Can't find any absolutely verified info about later builds, looks like the very latest patch build is H81022b from September and I'm going to assume if that happens to be on the board then all hope is lost, basically. Ugh...