Now you might want to keep charging until the red LED light of Librem 5 turns off. Actually, it is already some kind of ritual to keep on watching if Librem 5 is about to turn off by itself (at 2%). Do not wait that this happens again, just power off your Linux phone on time (especially if no power supply connected to it and/or you are not about to use it for more than twelve hours).
Some people are even much better organized, related to the same purpose: