Bare metal servers offered at Scaleway are at reasonable prices, which can be compared to those on Hetzner. You even get Proxmox installation by default contrary to Hetzner were you need to install Debian first. To setup Proxmox with one public IP anf pfSense with another one you need to order Flexible IP and request for virtual MAC address. Remember that on Scaleway’s flexible IPs gateway is fixed and it is 62.210.0.1. Then for the network configuration:

auto lo
iface lo inet loopback

auto eno1
iface eno1 inet manual

iface eno2 inet manual

auto vmbr0
iface vmbr0 inet manual
        address x.x.x.x/24
        gateway y.y.y.y
        bridge-ports eno1
        bridge-stp off
        bridge-fd 0
        pointopoint y.y.y.y
        hwaddress a:b:c:d:e:f
        up route add -net a.a.a.a netmask b.b.b.b gw y.y.y.y dev vmbr0
        up ip route add z.z.z.z/32 dev vmbr0
# PUBLIC

auto vmbr1
iface vmbr1 inet static
        address 10.0.0.1/8
        bridge-ports eno2
        bridge-stp off
        bridge-fd 0
# LAN

x.x.x.x is primary Proxmox public IP. y.y.y.y is its gateway (with a.a.a.a network with b.b.b.b netmask). z.z.z.z is then your secondary public IP (flexible IP) for pfSense firewall. As you can see, there are two network adapters, eno1 and eno2. First one (eno1) is used for public IPs and second one (eno2) is for internal network only. For some reason the same configuration as on Hetzner, concerning LAN networking, does not work, so there are few changes there over that configuration at Hetzner.