Hello,

I cannot realy help with this, but I was looking it the matter.
From what I understod, this menue item is a placeholder where you can put a link to a stem extracting software you have. The example given is for soeme phyton package.

There is an open source package phyton based called spleeter (byDeezer?) you can download (what you want to avoid). This requires to download and install phyton first, than you need an editor that works with that, than you need to download the spleeter code and then maybe complie it. A lenghty and cumbersome process than requires some knowledge. But that is free.

There are some online offers based on that spleeter code. You can upload a song and can then download the separated steems. Billed by song or on a subscription base. I would recommend to try with one song so you can judge the quality.

There is software available (e.g from Steinberg or iZotope) that can get better results, but they come at a hefty price tag (yet at least iZotope RX 9 offers a demo, the module you want is "musical rebalance"). Even those "pro" Versions cannot work miracles, yet it is close to a miracle what they can achive.
I myself have iZotope RX9 and if I put in some extra effort the result is astounding (extra effort in my case is applying melodyne to the vocal stem, "cleaning" it from artefacts, run the inverted result against the original mix and do a new separation.

One caveat here, the better the source, the better the result. Wave is better than mp3 and old tapes may not be the best source material. So a test with a one shot from an online service might be helping to compare expectacions with reality

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