I recently set up a Redmine install with PostgreSQL. By default, Redmine uses MariaDB or MySQL or at least the Bitnami stack I used does, I can’t remember which. But I chose PostgreSQL because I thought I saw somewhere that you needed PostgreSQL for one of the farmOS modules… I’m thinking something to do with the mapping or GIS module? Now I can only find one mention here of PostgreSQL and I can’t remember why in blazes I went with that. It’s working fine with my Redmine install and there were no problems setting it up, I just can’t remember why I went with it instead of the default. I have many projects in the works, so maybe I chose PostgreSQL for some other install I’m planning and I AM getting older and more forgetful, so maybe it’s some other software package entirely that required it. If anyone has any idea what I’m talking about, please refresh my memory so I can be returned to my regularly scheduled program. Thank you. 
Hi @Domhnall - for farmOS 1.x, MySQL/MariaDB is the “officially” supported database backend - so if you are starting out I would recommend that.
farmOS is built on Drupal, which supports PostgreSQL as well, and there have been a few people who have tried hosting farmOS on PostgreSQL. Unfortunately, there are one or two key queries (custom to farmOS) that are not currently PostgreSQL-compatible. It was my hope that we could fix those and declare PostgreSQL “officially” supported in farmOS 1.x, but I have not had the time to properly invest in that.
Furthermore, and worth noting, I am currently focusing on farmOS 2.x branch development (just in the beginning stages - not ready for use yet), and my intention is for farmOS 2.x to officially support PostgreSQL. I am doing all my development and testing with it right from the start. So, when it comes time to migrate from farmOS 1.x to 2.x, it will be a migration from MariaDB to PostgreSQL for many.
Hope that all makes sense. If you are able to, I would recommend using MariaDB to ensure that you have the best experience with farmOS 1.x.
I can’t for the life of me remember what it was I saw that made me think I should go with PostgreSQL. 
No problem, I’ll set up a MariaDB container with farmOS and then when I get a chance, figure out how to migrate my Redmine data from PostgreSQL to Maria. 
Thanks for the info!