Thank you for your fast reply.
Of course it was my own fault. Linux OpenVPN failed, because it strictly verified the VPN server certificate's CN, which was missing; Android/Windows were less strict. So I created a new VPN Server Certificate with CN field for OpenVPN role (Server) instance and then exported my personal client .ovpn profile. Now it works, also Android/Windows after updating .ovpn.
Of course it was my own fault. Linux OpenVPN failed, because it strictly verified the VPN server certificate's CN, which was missing; Android/Windows were less strict. So I created a new VPN Server Certificate with CN field for OpenVPN role (Server) instance and then exported my personal client .ovpn profile. Now it works, also Android/Windows after updating .ovpn.
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