With the upgrade to Mastodon 4.2.0, the way the search system works is changing to allow more broad searches across posts made across the fediverse.
Cutting to the chase: Full-text search across opted-in posts will be possible in the next few days.
In more depth, the system will allow you to search across your own posts and posts you've interacted with from others irrespective of their opt-in status for full-text search, but will additionally allow you to search ANY posts made by users that opt-in to allow their posts to be indexed.
To that effect, a new setting was added to the Public Profile > Privacy and Reach page called "Include public posts in search results" which is disabled by default. Turning this on will allow any user across the Fediverse to search and find your posts using full-text search.
For everyone else: There's Mastercard (Sorry not sorry xD) But, just take your instance's domain and add /settings/privacy to the end (e.g. https://INSTANCE.TLD/settings/privacy)
To allow our users to decide if this is a feature they want to use on their posts going forward, we won't be enabling ElasticSearch until Friday Sept. 22.
Additionally, new keywords will be added to the search system: