https://domcloud.co – Linux hosting service that also provides CI/CD with GitHub, SSH and MariaDB/Postgres database. Free version has 1 GB storage and 1 GB network/month limit and limited to a free domain.
https://filess.io - filess.io is a platform where you can create 1 database of the following DBMS for free: MySQL, MariaDB, MongoDB, PostgreSQL.
https://free-for.dev 검색하니 2가지 나오네요.