Kobo Libra 2 dead after 1 month of no use - no charge LED, no response

Looking for advice before I commit to a battery replacement.

My Kobo Libra 2 was working perfectly with no signs of battery degradation whatsoever. Normal charge times, normal runtime, no swelling, no issues. It then sat unused for about a month. Now it's completely unresponsive:

- No charging LED when plugged in (from any source)

- No response to short or long power button presses

- Screen stays blank, no "Powered off" message, no boot logo, nothing

What I've already tried:

- Multiple USB-C cables (data-capable, known good)

- Multiple power sources, including a 2A wall adapter (not just computer USB)

- Power button hold for ~30 seconds, then attempted reboot

- Left it plugged into the wall adapter overnight, no change in the morning

- Inspected the USB-C port, it's clean with no lint or debris, and the connector seats fully

Kobo support told me it's out of warranty and pointed me to iFixit as their repair partner. I understand iFixit doesn't currently stock a genuine Kobo battery for the Libra 2 specifically (only for the newer Colour models), so I'd be sourcing an aftermarket 305080 cell.

My questions:

1. Given that the device was fully healthy a month ago and just sat unused, does this sound like a deep-discharged battery latched off by the protection circuit, or could it be something on the motherboard?

2. Anything else worth trying before I open it up?

3. For the Libra 2 specifically, any tips on the battery swap? Recommended sources for a pre-wired 305080 to avoid soldering directly to the board? Anything to watch out for on disassembly?

Thanks in advance.