While a timeline is being defined for T180853: Bring a discourse instance for technical questions to production , we should consider the deprecation of https://www.mediawiki.org/wiki/Project:Support_desk in favor of https://discourse-mediawiki.wmflabs.org/
In order for this to happen, a plan agreed with the current maintainers of the Support Desk must be in place. This plan could include a transition, a freeze (leave pages not-editable, a possibility to come back if anything goes wrong...
Reasoning: The goal of https://discourse-mediawiki.wmflabs.org/ is to offer a central place for developer support and, in fact, technical support in general for Wikimedia and MediaWiki users. From all the channels where technical support is currently offered, Support Desk is the only one completely dedicated to developer support. The other ones are channels used for other purposes that also happen to offer technical support.