The issue seems to be that some USB drives won't mount during the booting if it is used, so OpenCore does not get to the picker screen. I don't think it is a graphics issue, as I tried disabling OpenCanopy to get back to the text picker but that didn't work either.
The main point seems to be that the OpenHfsPlus.efi is not fully tested, which is why the current Dortania Guide does not yet recommend it as a default driver:
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https://dortania.github.io/OpenCore-Install-Guide/ktext.html#firmware-drivers>