How to create a global language selector page at domain root with i18n when the global language has a prefix?
Consider creating a special "homepage" node, for which you set the "language" to "Language Neutral" (any path will do, even no path if that's what you'd prefer). And use its node ID (preceeded by 'Node/') as the value for "*Default front page *" within admin/config/system/site-information.

From then on, you can create any content for that node as your language selection page, which of course should include a link to each language specific "starting page".