Is there a way to include a Python interpreter in a kotlin app? I need to do some serial communication over WiFi and I thought a simple Android app will be good for this

There is Jython - still stuck at Python 2.7, but generally working. It can be used in both directions (e.g. Jython to Java and Java to Jython) - however it requires additional work, as it is intended for (desktop) JDK.
You might want to look at https://github.com/alsonkemp/..., but I haven't checked it.

Alternatively you can develop the app directly in Python, by using Kivy. However, the interoperability with Java/Kotlin classes is a bit... difficult, but generally working.