If you don't have an Adafruit style powerboost board around, or they're severely backordered (like now), an Alles PCB works great as a Powerboost. It supports lipo charging, 5V output, switches from wall power to battery power seamlessly and has a soft on-off switch for the 5V. very nice!
This is a repo i use when I need a powerboost and have more Alles PCBs than powerboosts around. prints battery status every few seconds to the UART, you can parse that on your MCU if you want!
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