On Meta there's a list of mailing lists that mentions "wikimedia-search", but that list seems to be dead and the archive is full of spam. Another list exists, called "discovery", but not listed on Meta. https://lists.wikimedia.org/hyperkitty/list/discovery@lists.wikimedia.org/
Indeed the Discovery https://lists.wikimedia.org/hyperkitty/list/discovery@lists.wikimedia.org/thread/HTEAZLNPUT3W3HTLAMP6B4AXKLXPSDSV/ list is the one I've seen get Search-related traffic. I wanted to update the relevant Meta page https://meta.wikimedia.org/wiki/Mailing_lists/Overview but got very lost when I saw the translate tag inside a row table template with an identifier (397). The list that's listed under Search and Discovery hasn't seen actual traffic from anyone on the search team in over 7 years. The discovery list I linked here is the appropriate substitute, if anyone knows how to edit that scary template thing.