MinT for Wikipedia Readers has hardcoded cxserver API URL at https://github.com/wikimedia/mediawiki-extensions-ContentTranslation/blob/a9aff125a5b26ac6e960485350bf5aaa2b61ee48/minT/src/useApi.js#L121 which prevents from pointing to a development/testing/staging version of cxserver
In CX, all API URLs should be based on $wgContentTranslationSiteTemplates configuration