I found I had a lot of problems getting my neo-6m to work when using Kstars. Ultimately for me it turned out to be a USB3 interference issue. As soon as I had my USB3 QHYCCD camera connected through a USB powered hub the GPS would never lock. Not sure if you have an RPI4 and this issue but if you do you could try extending the serial cable so the GPS is a couple of meters away. If you're not using USB3 for any thing then you can probably ignore this comment.

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