Hi,@Adolfo Garcia Welcome to the Microsoft Q&A forum, Thanks for posting your question.
I understand that you are using the TimescaleDB extension, which is not supported by the Single to Flex migration tool, and you are looking for guidance on how to complete the migration with this extension.
As per the Azure documentation on migrating from a single server to a flexible server, if you are using an extension that is not supported by the offline migration tool, you will need to raise a support request to complete the migration.
Please let me know if you need any help in raising a support case.
Regards
Geetha