My here linked post is surrounded with several other posts that are actually telling you that you need to boot your Linux phone without inserted battery. At same time suggesting to insert your Librem 5 battery back to charge from there, after hopefully/successfully booting into SMXO Librem 5 GUI and after logging into it.
If above isn’t helping with SMXO installation you would need to reflash your Linux phone back into PureOS, as purposely and kindly based on above @carlosgonz recommendation. And perhaps build SMXO locally (for Debian based distribution) from there, on top of PureOS.
Just use your Librem 5 power supply from now on until you get your inserted lithium-ion battery back to life. Especially if not really, really familiar with the PinePower technical specs when charging (or not) from there.
EDIT: @yogo1212, please stop using Librem 5 non-compatible power supplies there and simply follow (as no other way around known to me) this proper guide:
“The built-in BC1.2 compliance keeps the implementation clean and simple to use.” As further and thoroughly described here: https://www.analog.com/media/en/technical-documentation/tech-articles/overview-of-usb-battery-charging-revision-12-and-the-important-role-of-charger-detectors.pdf