Fix sql dump, Unknown collation: utf8mb4_0900_ai_ci | WebTechKitchen; Your Web Technology Kitchen, contact us to create, or maintain your websites and other digital properties.

sed -i '' 's/utf8mb4_0900_ai_ci/utf8_general_ci/g' backup.sql  
sed -i '' 's/CHARSET=utf8mb4/CHARSET=utf8/g' backup.sql

or this worked https://meetanshi.com/blog/error-1273-unknown-collation-utf8mb4-0900-ai…
just open the file and do %s/utf8mb4_0900_ai_ci/utf8mb4_unicode_ci/g