Is there any supported way to execute a Python script from a Premiere Pro UXP panel?

I'm not super familiar with UXP specifically, but I have some ideas on where you might need to look.

At least with extendscript, you can execute batch files like this, where inside it, it contains the call to the actual program and any parameters. I'm not sure if you're able to call extendscript methods from UXP but if so it could be an option:

var batFile = new File("C:\\Whatever\\Path\\WhateverBatch.bat")
batFile.execute()

More specific to UXP, I found this documentation which seems to show you can open a file with the default system app associated with it using an "openPath" method. So if you can't get it to execute the python script directly, I'd imagine you could use the batch file trick, where you put any parameters within the batch file.

Another trick I've used, is if you need the batch file to call some program dynamically with parameters, is to have the script write paramaters to a text file next to the batch file, then the batch file be set up to read from the text file.

The documentation link above also links to another docs page about a UXP "launchProcess" method. That's actually in the photohsop docs, but I'd assume it might be usable in premiere pro if it's linked from the premiere docs.