Setup additional IP address to Debian 12 VPS - following OVH guide but does not seem to

Hello,
I have just bought an additional IP address for my VPS. Debian 12 is installed on it.
I am trying to follow OVH guide but it is not clear: https://help.ovhcloud.com/csm/en-vps-network-ipaliasing?id=kb_article_view&sysparm_article=KB0047585#ubuntu-2004-debian-12

- My VPS primary IP address: 213.186.111.222
- My newly bought additional address: 51.75.88.22

* I did write 'network: {config: disabled}' into /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg

**First tentative**

1. I modified /etc/netplan/50-cloud-init.yaml to get this contant:

# 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}
network:
version: 2
ethernets:
ens3:
accept-ra: false
addresses:
- 2001:41da:743:1320::7f24/56
dhcp4: true
match:
macaddress: fa:34:31:93:4f:85
mtu: 1500
nameservers:
addresses:
- 213.186.111.222
search: []
routes:
- to: ::/0
via: 2001:41d0:701:1100::1
set-name: ens3

network:
version: 2
ethernets:
ens3:
dhcp4: true
match:
macaddress: fa:16:3e:7c:5f:63
set-name: ens3
ens3:
dhcp4: true
match:
macaddress: fa:16:3e:7c:5f:63
set-name: ens3
addresses:
- 51.75.88.22/32

2. I launched: `sudo netplan try`

** (process:45066): WARNING **: 19:53:32.871: Permissions for /etc/netplan/50-cloud-init.yaml are too open. Netplan configuration should NOT be accessible by others.

** (generate:45068): WARNING **: 19:53:32.884: Permissions for /etc/netplan/50-cloud-init.yaml are too open. Netplan configuration should NOT be accessible by others.
Cannot call openvswitch: ovsdb-server.service is not running.

** (process:45066): WARNING **: 19:53:33.856: Permissions for /etc/netplan/50-cloud-init.yaml are too open. Netplan configuration should NOT be accessible by others.
[]
Cannot find unique matching interface for ens3

** (process:45066): WARNING **: 19:53:34.050: Permissions for /etc/netplan/50-cloud-init.yaml are too open. Netplan configuration should NOT be accessible by others.

** (process:45066): WARNING **: 19:53:34.051: Permissions for /etc/netplan/50-cloud-init.yaml are too open. Netplan configuration should NOT be accessible by others.

3. `ping 51.75.88.22` does not seem to reach anything


**Second tentative**

1. I modified `/etc/netplan/50-cloud-init.yaml` to get this contant:

# 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}
network:
version: 2
ethernets:
ens3:
accept-ra: false
addresses:
- 2001:41da:743:1320::7f24/56
dhcp4: true
match:
macaddress: fa:34:31:93:4f:85
mtu: 1500
nameservers:
addresses:
- 213.186.111.222
- 51.75.88.22
search: []
routes:
- to: ::/0
via: 2001:41d0:701:1100::1
set-name: ens3

2. I launched: `sudo netplan try`

** (process:45975): WARNING **: 20:02:04.913: Permissions for /etc/netplan/50-cloud-init.yaml are too open. Netplan configuration should NOT be accessible by others.

** (generate:45977): WARNING **: 20:02:04.922: Permissions for /etc/netplan/50-cloud-init.yaml are too open. Netplan configuration should NOT be accessible by others.
Cannot call openvswitch: ovsdb-server.service is not running.

** (process:45975): WARNING **: 20:02:05.843: Permissions for /etc/netplan/50-cloud-init.yaml are too open. Netplan configuration should NOT be accessible by others.

** (process:45975): WARNING **: 20:02:06.026: Permissions for /etc/netplan/50-cloud-init.yaml are too open. Netplan configuration should NOT be accessible by others.

** (process:45975): WARNING **: 20:02:06.027: Permissions for /etc/netplan/50-cloud-init.yaml are too open. Netplan configuration should NOT be accessible by others.
Do you want to keep these settings?


Press ENTER before the timeout to accept the new configuration


Changes will revert in 60 seconds

3. `ping 51.75.88.22` does not seem to reach anything


FYI: I have changed all IP and MAC address of my message.