Firewall / Ip rule issues between two hosts via vSwitch

I have two servers in play here, one is a Qemu VM host, the other being a storage box of sorts.

They are hetzner machines, and I have them connected via a vSwitch.

Server1 vSwitch interface:

3: local@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 10:7b:44:b1:5b:7d brd ff:ff:ff:ff:ff:ff
    inet 192.168.100.1/24 brd 192.168.100.255 scope global local
       valid_lft forever preferred_lft forever

Server1(VM host) ip route:

default via <redacted-public-ip> dev eth0 proto static metric 100 
<redacted-public-ip> dev eth0 proto static scope link metric 100 
192.168.10.0/24 dev virbr0 proto kernel scope link src 192.168.10.254 metric 425 <-- virbr0 network
192.168.10.253 via 192.168.100.2 dev local <-- srv02 IP to fit in virbr0 net space

Server2 vSwitch interface:

3: local@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1400 qdisc noqueue state UP group default qlen 1000
    link/ether 08:60:6e:44:d6:2a brd ff:ff:ff:ff:ff:ff
    inet 192.168.100.2/24 brd 192.168.100.255 scope global local
       valid_lft forever preferred_lft forever
    inet 192.168.10.253/24 brd 192.168.10.255 scope global local
       valid_lft forever preferred_lft forever

Server2 ip route:

default via <redacted-public-ip> dev eth0 proto static metric 100 
<redacted-public-ip> dev eth0 proto static scope link metric 100 
192.168.10.0/24 dev local proto kernel scope link src 192.168.10.253  <-- to access virbr0 via vSwitch

I have the routes setup correctly, I guess - since everything works a-ok with the firewalld service off.

However, if I turn it on, the issues start.

These are the firewall zones on Server1 (on which when I disable firewalld everything works)

libvirt (active)
  target: ACCEPT
  icmp-block-inversion: no
  interfaces: virbr0
  sources: 
  services: dhcp dhcpv6 dns ssh tftp
  ports: 
  protocols: icmp ipv6-icmp
  forward: no
  masquerade: no
  forward-ports: 
  source-ports: 
  icmp-blocks: 
  rich rules: 
    rule priority="32767" reject


public (active)
  target: default
  icmp-block-inversion: no
  interfaces: eth0 local
  sources: 
  services: cockpit dhcpv6-client ssh
  ports: 
  protocols: 
  forward: no
  masquerade: no
  forward-ports: 
  source-ports: 
  icmp-blocks: 
  rich rules: 

I have tried turning on masquerade on each of those, both of those at the same time, to no avail. I am "testing" this with a simple ping from Server2, toward one of the VMs on virbr0

Is there anything obvious that I am missing here ?

Thank you all in advance.