Unable to connect VM to internet with one additional IP (Hetzner dedic)

Host's enp0s31f6 is bridged to vmbr0 and has the same IP address. This will not work (a bridged NIC should never have an IP address). AFAIU in case of "routed solution" you must not bridge the physical NIC; however for provider specific issue contact their forum.

In general it helps to follow IP packets (when e.g. runing a ping) via tcpdump.
 

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