Trying to use a tunnel from HE but some IPv6 connectivity is broken

I have a server from Kimsufi (OVH Eco branch) but unfortunatelly they only provide a /128 IPv6 block.

So, I decided to use a Hurricane Electric (HE) tunnel to have a /64 IPv6 block.

I've followed HE instructions in how to set up the tunnel, etc, but somehow some IPv6 connectivity is broken.

Current main config - 50-cloud-init.yaml

# This file is generated from information provided by the datasource.  Changes
# to it will not persist across an instance reboot.  To disable cloud-init's
# network configuration capabilities, write a file
# /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following:
# network: {config: disabled}
###
# default config - 50-cloud-init.yaml
###
network:
  version: 2
  ethernets:
    eno0:
      set-name: eno0
      accept-ra: false
      dhcp4: true            
      dhcp6: false
      gateway6: 2001:470:1f20:a::2
      match:
        macaddress: 00:22:4d:84:93:df
      nameservers:
        addresses:
          - 8.8.8.8
          - 8.8.4.4
          - 2001:4860:4860::8888
          - 2001:4860:4860::8844
      addresses:
      # Routed /64: 2001:470:1f21:a::/64
        - 2001:470:1f21:a::1/64
        # James
        - 2001:470:1f21:a:ef54:7bad:b8b0:801d/64
        # LikeIcare
        - 2001:470:1f21:a:6e0c:b070:c4cc:619c/64
        # Lounge
        - 2001:470:1f21:a:35f1:20bb:67b2:efce/64
        # ApexBNC
        - 2001:470:1f21:a:9df3:0c29:2cca:036e/64
        # Relays
        - 2001:470:1f21:a:a239:ca6e:c932:c379/64
        # weechater
        - 2001:470:1f21:a:4384:4ba6:36be:d16d/64
        # Scheherazade
        - 2001:470:1f21:a:7cc5:506f:d124:345a/64
        # RiberHus
        - 2001:470:1f21:a:7966:7232:e0ca:8ccc/64
        # Vigilante
        - 2001:470:1f21:a:6171:fd09:929e:72e2/64
        # Gitnotifier
        - 2001:470:1f21:a:3b98:2cc0:dd51:2e16/64
        # BloodyMary
        - 2001:470:1f21:a:0612:5d3c:78d2:3b5e/64

Current tunnel config - 99-he-tunnel.yaml

network:
  version: 2
  tunnels:
    he-ipv6:
      mode: sit
      remote: 216.66.87.102
      local: 5.135.186.51
      routes:
       - to: default
         via: "2001:470:1f20:a::1"
      nameservers:
        addresses:
          - 2001:4860:4860::8888
          - 2001:4860:4860::8844
      addresses:
        # Client IPv6 Address
        - 2001:470:1f20:a::2/64

Warnings with current configurations

** (generate:4594): WARNING **: 13:57:50.895: `gateway6` has been deprecated, use default routes instead.
See the 'Default routes' section of the documentation for more details.
 
** (generate:4594): WARNING **: 13:57:50.897: Problem encountered while validating default route consistency.Please set up multiple routing tables and use `routing-policy` instead.
Error: Conflicting default route declarations for IPv6 (table: main, metric: default), first declared in he-ipv6 but also in eno0
 
** (process:4592): WARNING **: 13:57:53.256: `gateway6` has been deprecated, use default routes instead.
See the 'Default routes' section of the documentation for more details.
 
** (process:4592): WARNING **: 13:57:53.259: Problem encountered while validating default route consistency.Please set up multiple routing tables and use `routing-policy` instead.
Error: Conflicting default route declarations for IPv6 (table: main, metric: default), first declared in he-ipv6 but also in eno0
 
** (process:4592): WARNING **: 13:57:53.311: `gateway6` has been deprecated, use default routes instead.
See the 'Default routes' section of the documentation for more details.
 
** (process:4592): WARNING **: 13:57:53.314: Problem encountered while validating default route consistency.Please set up multiple routing tables and use `routing-policy` instead.
Error: Conflicting default route declarations for IPv6 (table: main, metric: default), first declared in he-ipv6 but also in eno0
 
** (process:4592): WARNING **: 13:57:54.629: `gateway6` has been deprecated, use default routes instead.
See the 'Default routes' section of the documentation for more details.
 
** (process:4592): WARNING **: 13:57:54.630: Problem encountered while validating default route consistency.Please set up multiple routing tables and use `routing-policy` instead.
Error: Conflicting default route declarations for IPv6 (table: main, metric: default), first declared in he-ipv6 but also in eno0
 
** (process:4592): WARNING **: 13:57:54.631: `gateway6` has been deprecated, use default routes instead.
See the 'Default routes' section of the documentation for more details.
 
** (process:4592): WARNING **: 13:57:54.631: Problem encountered while validating default route consistency.Please set up multiple routing tables and use `routing-policy` instead.
Error: Conflicting default route declarations for IPv6 (table: main, metric: default), first declared in he-ipv6 but also in eno0

When I try curl -6 https://nominatim.openstreetmap.org the connection just times out.

Using mtr -6 nominatim.openstreetmap.org on terminal only has the following as output: mtr

Any help is highly appreciated.

Thanks in advance