Starting in Mastodon 4.2.0, you can filter your searches on Mastodon by language.
As no one else has done it, I've written an easy-to-use list of all the language codes used on Mastodon:
➡️ https://fedi.tips/language-codes-used-by-mastodon/
Combine these codes with the operator language: to filter your search results.
For example, if you only want Mastodon search results in French you would include language:fr in your search alongside the keywords or hashtags that you're looking for.
GNU social JP is a social network, courtesy of GNU social JP管理人. It runs on GNU social, version 2.0.2-dev, available under the GNU Affero General Public License.
All GNU social JP content and data are available under the Creative Commons Attribution 3.0 license.