[T-Mobile LG G4] pianoplayer88key:
So ... the freezer method has worked (with the phone in a Ziploc bag), at least partially. After turning off WiFi, a few days ago I was able to use ES File Explorer (already installed) to copy the internal phone memory to a 128GB SD card which was only about 10-20% full or so. (I couldn't copy absolutely everything, as my G4 isn't rooted yet.) I did it in stages - first copied several user data folders just in case it croaked mid-backup (it didn't), then did the rest.

Just earlier this morning, I used SuperBackup+ (or whatever it's called, I forget atm & the phone's charging again) to back up a few more things.

Then I went into the settings to see if anything was set to back up to the cloud, or could be backed up. Under "Backup and Reset", it was set to back up to my Google account. I also checked a few other settings.

Right before turning on WiFi again, I opened CPU-Z, to find most of the temps around 8°C. After turning WiFi back on, within seconds most of the temps shot up to the 30s to 60s °C, and the top 2 on the list (which included battery) pegged at 140°C, then the phone rebooted itself. So apparently turning WiFi on quickly overwhelms the phone. (I can't use mobile data, as I took the SIM card out and am using it in my SGH-T699 for now.) It then started up briefly, and while I *think* I may have been able to turn off WiFi again before it rebooted again, it started looping, from what I could tell. (Was probably time to take a break anyway, as I'd been standing there for a good 10-15 minutes or so with the freezer door open.)

I'm still hoping I might have a little bit of life left for backing up, after giving the phone a rest, battery a charge, letting the freezer settle down, and refreezing the phone.

One more thing I'd like to do with the phone - root it. Is there a way to do it without an internet connection, if possible without a computer (although maybe I could shut the freezer door on the USB cable), and for sure without wiping the device? I'd really like to use Titanium Backup Pro (already installed) to back everything up to the 128GB SD card.

Also I've heard about possibly disabling the two fast CPU cores, but also heard that may only work on Lollipop. (My G4 has Marshmallow installed.)

Anyway, right now the phone is plugged in (out of the freezer) and charging again. Interesting thing though ... while it was powered on in the freezer, it was saying I had 51% battery left. (This was right after I'd pulled it off the charger and it said 98-100% or so - the powered-off battery meter.) Then, plugging it back in (again powered off), it said 78%. Is the huge discrepancy in battery percentages temperature related, or indicative of another issue like a weakening battery? (The battery hasn't swelled at all, from what I can tell.)

I think it's time for a new phone soon, though. I might make another topic with more details, but a few I'm looking at maybe are the Asus Zenfone AR, Google Pixel, OnePlus 3T, Samsung Galaxy S7, maybe a few others. (I'm not as sure about the LG G6 or V20.) Other brands under consideration include HTC, Huawei, LeEco, Motorola, Oppo, vivo, Xiaomi & ZTE.

Basically I'd like something that

officially supports rooting / custom ROMs (and stock ROM is as close to vanilla Android as possible),

is officially supported for updates for a good while (for example if it comes with Android 7, I can upgrade to 9 or if possible 10 OTA, and beyond with community-made ROMs),

has a decent CPU/GPU (like SD 820/821/835 & Adreno 530/540),

plenty of RAM (6+ GB),

a decent amount of internal storage (64+ GB),

has either a micro SD slot or supports USB OTG or both,

among other things.

I'm guessing the 1+3T might be the best compromise? (Or stretch the budget & get the Pixel?) Or should I maybe consider waiting for the Pixel 2 or the OnePlus 4/5? Or get one of the other options / something else entirely? (I'd like to buy within the next month or two, if not sooner.) I had been planning to upgrade my desktop PC to AMD Ryzen 7, but figured I'd use the $ I would have spent on that, on the phone instead. (I can limp along on my i7-4790K a while longer, or my laptop's i7-6700K, etc, it'll just be somewhat slower in video editing, multitasking, etc. From what I hear my i7s are maybe faster at 1080p gaming, but I don't game all that much.)

I'm on T-Mobile - the $30/month 5GB+100min plan for now, but eventually tentatively plan to upgrade to unlimited with the unlimited hotspot addon.