I confirm the sibling post that adding a column is instaneous on MySQL 8 (although there are limitation), and point to the reference document: https://dev.mysql.com/doc/refman/8.0/en/innodb-online-ddl-op....
Outside the context of db comparisons, and in relation to the specific case, if you don't have triggers/foreign keys on a given MySQL table, Gh-ost¹ solves the DDL locking issues.