https://www.sic-info.org/wp-content/uploads/2014/02/easy_japanese.pdf
https://www.nhk.or.jp/lesson/ja/
"Easy Japanese"
https://www.city.osaka.lg.jp/shimin/page/0000510655.html
「やさしい日本語」という言葉をご存じですか？
「やさしい日本語」は、外国人の方など日本語があまり得意でない方に伝えるため、
わかりやすい言葉や表現に言い換えた日本語のことです。
https://www.japantimes.co.jp/opinion/2019/10/25/commentary/japan-commentary/communicating-foreign-residents-plain-japanese/
https://www.japantimes.co.jp/opinion/2019/08/13/commentary/japan-commentary/multilingual-support-foreign-residents/
https://www.japantimes.co.jp/news/2005/01/15/national/disaster-alerts-to-be-in-easy-japanese/
Japan Times calls it "plain Japanese" in the 1st link (2019) but "easy Japanese" elsewhere (2019, 2005)

https://mainichi.jp/english/articles/20200721/p2a/00m/0na/021000c
The "easy Japanese" movement began as a means to let foreigners, who are not fluent enough in Japanese or English, know what to do in times of emergency by providing evacuation information during disasters among other guidance in friendly expressions that are easy to understand. Research on the matter began in the wake of the Great Hanshin Earthquake that devastated Kobe in western Japan and surrounding areas in 1995. Many foreigners also fell victim to the disaster, and there were people who could not obtain necessary information due to language barriers.

やさしい日本語	11288	88.6%
優しい日本語	989	7.8%
易しい日本語	458	3.6%