Invalid language tag after updating to 1.6.0

As mentioned before, here my issue in a separate topic:

Invalid language tag: “de-DE_formal”

in AnalyticsDashboardWidgetPopularPagesTable
in NewComponent
in FilteredComponent
in FilteredComponent
in WithFilters(DashboardPopularityInner)
in DashboardPopularity
in FilteredComponent
in FilteredComponent
in WithFilters(DashboardModule)
in DashboardModules
in DashboardMain
in div
in div
in div
in div
in ErrorHandler
in DashboardApp
in ErrorHandler
in GoogleSitekitDashboard

When I copy the Locale, this is the output:
{
“siteKitLocale”: {
“domain”: “google-site-kit”,
“lang”: “de_DE_formal”
},
“browserLocale”: “de”
}

Thanks for your support!