Remove the battery and plug the phone to a USB-A source using A-to-C cable. Try both plug orientations. Look for any signs of life (LED, vibration etc.).
Find a universal battery charger and charge the battery up a bit (no higher than 4.2V though). Then put it back into the phone and try to boot.
Not sure if my previous experiences will help you. I too had a “dead” Librem 5 after convergence/overheating/Nexdock snafu. The only way to revive was to flash it.
Unless you have vital data to lose it might be worth a try. You could then even try Mobian or PostmarketOS to avoid the wait for Crimson.
I think that holding down the power button for a very long time (more than 20 seconds, better make it 30 to be on the safe side), can make the phone exit from some weird state it got into. Then release the power button and hold it down again, then it starts to boot up after a few seconds. All this with the battery in the phone, and without any charger connected. (You may need to charge the battery first, then unplug the charger, then hold the power button for 20+ seconds, then releast it and hold it for a few seconds again.)
Contrary to the instructions for the Librem 5 on the GitHub repository, run boot-purism-librem5.sh first, put the Librem 5 into flash mode by holding the volume up button, then simultaneously hold the power button for one second. If you successfully have Jumpdrive running on the Librem 5, you can backup its partitions and/or reflash it thereafter.
I had a messed up L5 recently (few months ago) that appeared dead as described here basically, but which somehow still booted via Jumpdrive as described by Frankly.
No idea if that situation was specific to me, but I was sure glad to see the L5 screen light up with the Jumpdrive stuff
Yes, holding power button for more than 18+ seconds with some power supply (to me unknown one or even with the originally distributed one that is able to offer/negotiate higher voltages) connected to the Librem 5 USB-C charging port should be avoided at all times, IMHO.
This important message confirms my here related thoughts (any smartphone without inserted battery might …) :
And, as closely correlated, it is as well important not to translate wrongly (nor try something that is not recommended somewhere/anywhere) what knowledgeable people precisely wrote or rather directly, besides politely, recommended:
It doesn’t have to be “avoided”, it just won’t do anything. The hard reset that happens about 18s after holding the button (equivalent to taking the battery out for a moment and putting it back in) only works when no power is provided over USB-C, as it only cuts the battery power path out.
There’s no point in doing it with no battery connected either.
@NyxTheNightHerself how did it go, did you try any of the suggestions in this thread, did you manage to finally bring the apparently-dead L5 back to life?
Ultimately I was able to boot it, yes. I got an aftermarket universal battery charger and charged my batteries with it, and the phone booted normally. Apparently the batteries were so discharged that the phone would not charge them.
I’m still very confused as to why it wouldn’t boot on external power, though that is less of an issue for now.