There are a couple things you will need to account for, but it should be possible to use those two boards together.
A single cell LiPo will be around 4.2V at maximum charge, which is too low for the Maestro, which has a minimum operating voltage of 5V. You could either use a separate power source for the Maestro that is in the appropriate voltage range (5-16V) or you could use a step-up voltage regulator to boost your supply voltage high enough for the Maestro.
When using a 3.3V and 5V device together in the same system, there are 2 things to consider: is the 3.3V device 5V tolerant and can the 5V device read 3.3V signals. If the pins on your 3.3V device are not 5V tolerant or the 5V device will have problems reading the 3.3V signals, you can use a bidirectional logic level shifter between the devices to make sure they receive the appropriate voltage levels.
While the Maestro is not guaranteed to read 3.3V as a high signal, it usually works okay, but if you want to ensure reliable operation, you should boost it. From a quick search on Adafruit’s website, it sounds like none of their Feather boards are guaranteed to be 5V compliant and they recommend only using 3.3V signals. So it sounds like using a logic level shifter is appropriate in this case.
By the way, sometimes one of those constraints can be bypassed if you do not need bidirectional communication. For example, if you just want to send TTL serial commands to the Maestro, but do not need the Maestro to send anything back in response, you can omit the connection between the Maestro’s TX pin and your controller’s RX pin.