That's a post from 2019, so of course Proxmox will not be on therehttps://www.veeam.com/blog/backup-replication-community-edition-features-description.html
Veeam Community Edition, only works with VMware, HyperV and AHV. To use Veeam with Proxmox, you need a License.
Judging by this reddit user (not tested it myself) it IS possible/available on the community edition (after a few rounds of updates/upgrades/reboots).
https://www.reddit.com/r/Proxmox/co...=web3xcss&utm_term=1&utm_content=share_button
Looking at the error-log though, it LOOKS like you are trying to add something named
virtıo0
which is a very strange name, as it contains an i without a dot in it (see below)
virtio0
I'm however not sure if that is a bug in the Veeam-code, or a bug in something you selected/typed (in either Veeam or Proxmox)