Normally you can do that in two ways both need to be done in luci.
The less secure one:
If you go to luci -> network -> firewall set to zone wan everything on accept.
more secure:
if you go to luci -> network -> firewall -> traffic rules tab
there you can create a rule with more fine control to ports etcetera.
note that the source zone is the zone your traffic orginates from in your case flints 2 lan, and destination wan.
if the above still doesn't work, you have to look into the dhcp settings in luci.
In normal circumstances a bridge maybe only has one ip you can go better use the traffic rules, also if it was configurered like DMZ would do its better to have it more restrictive.
Then again there are different variations of what a 'bridge mode' could be
@alzhao, goal is to have home lab behind GL-INET router, nevertheless when away from home i want to be able to access ISP router from GL-INET router wireguard, or any other device that make sense to be in that subnet.
It didn't work for me, I have an ont behind my mt6000 that I have access to via 192.168.0.1 in the settings you provided, I don't have access, changing it of course to my respective IP.