f9p is a dual frequency chip. however both rtklib v2.4.2 and v2.4.3 can not decode L2 signal from ubx format. so if you set the frequency to L1+L2, you will not get solution. you can set bands to L1 only, or use the version from rtkexplorer, which can decode l2 signal. rtklib on rasbian only have command line interface, and is not very similar to windows version. I hardly only use rtklib on rasbian, so I do not exactly understand your problem.
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