If you get this error in your logs:
add bridge failed: Package not installedThis error normally means one of two things.
On Mint/Debian check for "brctl". If it's not there do
sudo apt install bridge-utils uml-utilities
On some installs I have seen that you cannot modprobe bridge.ko (it fails) because your list of dependencies is broken for some reason.
Do this to restore a list of modules:
Then try to modprobe bridge again
eg: linux-modules-extra-generic linux-modules
brctl addbr br0