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As I can see, there is a feature request to enable support for Postgres SQL 12. You can check the feature request:
I strongly recommend voting and watching the issue above. However, it doesn't mean that Atlassian will definitely implement it, but it will be used to keep track of the features that are requested and then analyzed if they will be implemented or not.
Also, it is important to note that Atlassian will discontinue "Server" products and stop functional updates for all "Server" edition products soon. So, they might provide this functionality only for "Data Center".
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