Sorry, for the late reply. I am currently trying a different solution. This issue seems to be related to conda. At least that's what the PyInstaller developer assumes. I'll get back to you if I have run more tests :).

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I ended up using PyInstaller directly. codesign runs with normal speed here.

Yes, because this way i make sure PyInstaller is making an x86_64 app (could also do this with a flag, but I prefer it this way. But actually maybe I should try it using the flag and not Rosetta. Did this especially for creating a venv so that pip installs the correct packages).

OK, I cannot run PyInstaller from my -x86_64 env successfully in an arm64 shell, so it looks like at least for this stepp I need Rosetta2.

By the way, what is this weird rosetta error? Is it really rosetta (1) or rosetta2?

You can check the currently selected version using xcode-select -p.

Is there a way to get this info in an python based app?

You’re welcome :). In the meantime there are also pip wheels for arm64 available.