If it helps, here’s my network setup. It’s a little complicated because I use VLANs (10=main LAN, 11=guest, 12=IoT, 13=test) so I build 4 bridges, one for each VLAN. The naming scheme I use possibly isn’t needed any more, but it matches what it used to look like on C7, so I’m sticking with it.
Only VLAN 10 gets an IP address 'cos that’s how I access the machine.
Now I can put VMs on any (or all) networks.
nmcli connection delete enp1s0.10 enp1s0.11 enp1s0.12 enp1s0.13 br-lan br-guest
br-iot br-temp
nmcli connection modify enp1s0 ipv4.method disabled ipv6.method disabled
nmcli connection add type bridge con-name br-lan ifname br-lan bridge.stp no ip4 10.0.0.133/24 gw4 10.0.0.1 ipv4.dns "10.0.0.1 10.0.0.5" ipv4.dns-search "spuddy.org" ipv6.method disabled
nmcli connection add type bridge con-name br-guest ifname br-guest bridge.stp no ipv4.method disabled ipv6.method disabled
nmcli connection add type bridge con-name br-iot ifname br-iot bridge.stp no ipv4.method disabled ipv6.method disabled
nmcli connection add type bridge con-name br-temp ifname br-temp bridge.stp no ipv4.method disabled ipv6.method disabled
nmcli connection add type vlan con-name enp1s0.10 ifname enp1s0.10 vlan.parent enp1s0 vlan.id 10 slave-type bridge master br-lan
nmcli connection add type vlan con-name enp1s0.11 ifname enp1s0.11 vlan.parent enp1s0 vlan.id 11 slave-type bridge master br-guest
nmcli connection add type vlan con-name enp1s0.12 ifname enp1s0.12 vlan.parent enp1s0 vlan.id 12 slave-type bridge master br-iot
nmcli connection add type vlan con-name enp1s0.13 ifname enp1s0.13 vlan.parent enp1s0 vlan.id 13 slave-type bridge master br-temp
I like the old bridge-utils for seeing things, so this is the result
% brctl show
bridge name bridge id STP enabled interfaces
br-guest 8000.b0416f0e52ab no enp1s0.11
v-pinky9-guest
br-iot 8000.b0416f0e52ab no enp1s0.12
v-pinky9-iot
br-lan 8000.b0416f0e52ab no enp1s0.10
v-pinky9
v-plexserver9
br-temp 8000.b0416f0e52ab no enp1s0.13