According to :ref:ex-source-loc-methods, the DICS beamformer at least only accepts a single channel type at a time. Since the covariance can be computed for both meg and eeg, that can be passed to apply_lcmv but then the filter channel names only include the meg channels so I assume the eeg channels are tossed. It seems that there should at least be a warning but probably more appropriately a NotImplementedError when eeg channels are passed that they will not have corresponding filters returned. cc @britta-wstnr