The Power Platform admin center seems to work differently than any other admin center in 365 in that you can't change user language. In the Power Apps Portal you can change language by clicking on the cog wheel and Power Apps Settings, the same for other admin portals. That does not exist work the Power Platform admin center, it solely bases it language setting on the browsers language settings (for Edge the language that is on top of the preferred language list.

This should work as in every other place that you can change the language and only the default setting should default to browser language.

English is definitively preferred for troubleshooting but i might want another language for other sites I visit.