@viragomann
Thank you anyway for your help. This allowed me to identify the problem and better diagnose a routing problem.
For my part, I carried out some test and I saw the change.
In the routing table, without a gateway, the "use" column remains at 0.
When I put the Proxmox gateway, some traffic seems to be detecting.
I think it's a routing or NAT problem.
Gateway :
gw.PNG
Route :
route ok.PNG
According to this tutorial (in French), it should however work.
The only difference is, potentially, the / 32 mask.
https://voiprovider.wordpress.com/2017/03/26/la-ha-avec-pfsense-et-1-seule-ip-wan/
I will probably create another post in the "routing" category with a link to this post.