It seems the host defaulting as localhost has not worked for people in at least two instances
The documentation says to set as localhost whereas it seems to default to meilisearch and that does work
References:
https://misskey-doc.7ka.org/ja/misskey/enable-meilisearch
https://discord.com/channels/1126590789322035230/1163467816284991591/1291157680840507454
https://discord.com/channels/1126590789322035230/1163467816284991591/1281352518928175164