Try to calibrate the battery with very simple means.
Without going into the basics of how batteries work, just this: Every battery has a smart chip. This chip sends a signal that indicates the current state of charge of the battery. When the battery is 0% fully discharged and then 100% fully charged, this smart chip “learns” the capacity.
First completely empty the battery of your device. So do not charge it at any time and wait until it shuts off. Once it has turned off, restart it so that it turns off again. Although the battery is at 0%, there are still some reserves. Now charge the phone to 100% while it is switched off. Make sure that the full 100% is reached.
Once the battery is fully charged, disconnect the phone from the power source and restart it. This cycle of fully discharging and recharging allows the smart chip to calibrate its readings with the battery charge cycle.
Have you ever tried another custom ROM based on LineageOS 16.0 for microG and found the same bug “turn mobile data (LTE) on”?