According to the StarbaseModuleDefs, the Enjoyment tech should give the Altarians access to the starbase Recreation Center Module, but the benefit is not listed in the ingame tech tree, and you can't build it on starbases after researching the tech. It turns out that <Option>Enjoyment</Option> in StarbaseModuleDefs needs to be changed to <Option>EnjoymentTech</Option> - this fixed the problem for me after starting a new game.