Using iPhone 2020 battery replacement kit from ifixit
After putting everything back together, the first time I got nothing from the phone, so I took it apart again to check for any mistakes and I did see a ribbon cable (the one one closer to the bottom outside edge) got a little caught on the when reassembling, so I got that straightened out so it wouldn't catch, and I managed to get to the critical low battery screen (before boot). I haven't really been able to get past this point despite charging both wired and wirelessly. The low battery screen seems to last its full cycle, but after that it doesn't respond to power button or anything. Tried hard reset sequence as well and nothing.