Yeah we would like to see this too, as being limited to only 1 database type limits our hosting needs

As we can only use Microsoft SQL Server and features are limited in AWS RDS, where we are required to host it

We are using SQL Server Web but if we want HA requires SQL Server Standard which ends up a lot more expensive just so we have HA which is available with every other DB type

This would be really useful, especially now that you are releasing a containerized version for Linux - many companies don't want to introduce a Microsoft technology stack if that's not their thing - so having support for at least one other non Microsoft database would be a nice addition. I'm facing an uphill battle and the reason is my organization doesn't want to add a SqlServer database. PostgreSQL would be great or MySQL.

Is there a concern or problem using SQL Server? Supporting other RDBMS would add a load of additional development, maintenance and support overheads so would be an unlikely option unless there are important issues. If it is a problem with installing and managing this peice of infrastructure is it possible to just use Microsoft Azure SQL Database or AWS RDS SQL Database?
https://octopus.com/docs/installation/sql-server-database-requirements#SQLServerDatabaseRequirements-Supportedversionsandeditions