When trying to use peer-groups for neighbours, if you also have parameters default 'no-ipv4-unicast' set vyos will not create the neighbour:
set protocols bgp 65400 parameters default 'no-ipv4-unicast' set protocols bgp 65400 peer-group TEST remote-as '65401' set protocols bgp 65400 neighbor 10.0.0.2 peer-group 'TEST'
[ protocols bgp 65400 ] [ protocols bgp 65400 neighbor 10.0.0.2 ] peer-group defined but ipv4-unicast is disabled
Looks to be caused by a check here:
I'm not sure exactly why this check is there, it seems erroneous to me. Commenting out lines 1426 - 1428 seems to make vyos behave