That's another post that is here more to be a reminder to me that to be really usefull or add important informations.
Since I am migrating to a new VPS and I'd like to keep my personal stuff separated from the other sites I hosted on my server, I decide to get 2 IP addresses to use.
Then the problem is how to use both of them: well, really simple.
The new installation uses Archlinux and the default systemd-networkd, so once I created the file for the interface, I just needed to add another
Address = line to it to use the second IP.
The end results is something like:
[Network] Address=your_first_ip Address=your_second_ip Gateway=your_gateway DNS=your_dns
and just restart. That's all. Really. (I was afraid it would be way more complicated to be honest)