The /list is hiding some channels at the DALnet network.
Channels starting with #0! are hidden from the list for some reason.
Ever since version 7.68 the "[x] Hide non-text channel" option was removed, so those channels now are hidden with no recourse to display them on the channels list.
02/04/2022 - mIRC v7.68
33.Removed List Channels dialog lock option as this has been
superseded by the Lock feature in the Options dialog, and the
hide non-text channels legacy option.