Use https://dbeaver.io/ , as An Le mentioned.
After 40 years of DB development, migrating DB data is still a challenge. DBeaver is a free tool to use for data migration. But you still have to migrate the schema.
Exporting data from DBeaver
From contextual menu of your SQLServer database or schema select Tools > Create new Task > Common > Data Export
You will generate SQL insert files or CSV files. For migration between database types use CSV files.
Cons of SQL Server Migration Tool
Unable to migrate rows containing booleans.
Export ended up in errors of migrationg data with Bool columns, complaining that value is not boolean, although both source and destination columns where of boolean type.
Unable to continue with the next tables afer one table migration fails.
SQL Server - A single error stops all migration even for tables that are not related to the initial error.
Configuring the tool over and over again, trying to export your data is a waste of time. SQL Server migration task does not save the configuration of the source and destination connections. And the wizard is not user friendly, spending your time on it is frustrating. I assume the migration project was abandoned for at least 10 years.