Windows 11 does not accept DNS over HTTPS templates without a trailing slash (”/”). For instance, Windows 11 will accept https://dns0.eu/ but refuse https://dns0.eu.
Help us fix this for everyone by asking Microsoft to accept DNS over HTTPS templates without a trailing slash. You can easily submit a feedback on their Feedback Hub.

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Workaround

Make sure you include a trailing slash when entering the DNS over HTTPS template.