Content and Section Translation use Machine Translation (MT) as a starting point. Multiple services are available for different languages, and a configuration file determines the default for each language pair.
We set those defaults based on input from the communities, but when there is no explicit setting, alphabetical order is followed. This may result in services being exposed as the default where they are other options that are generally considered fo a higher quality.For example, French editors reported issues because Elia became the default over Google for the en-fr language pair (T284900#7186502).
In order to support this, a general order of preference can be defined. In this way, a default priority is defined that can be overwritten by specific rules. A possible ordering that gives priority to open source services and a general sense of translation quality could be: Apertium, OpusMT, Google Translate, Yandex, LingoCloud, Youdao, Elia (we may need to review current defaults, data, and community feedback to confirm a final ordering).