Hello,
Currently installing two BR1 mini routers. Looking at the BGP configuration options I do not see an option in the advertise custom network to specify a default route. This would be do to the limitation of specifying a /0 subnet mask. Very surprised why the mask option of /0 was not listed.
Use case is I have two BRI connected over an ethernet link and I want to advertise the default from RT2 → RT1. See diagram. Should be trival to do by updating the custom network advertisement to allow a /0 in the drop down mask