It looks like this command does nothing.
set protocols bgp 65001 neighbor 2001:0DB8:0:AAAA::1 address-family ipv6-unicast capability dynamic
There is no handler for it on Perl
https://github.com/vyos/vyatta-cfg-quagga/blob/crux/scripts/bgp/vyatta-bgp.pl#L233-L252
And not FRR commands for afi ipv6
r4-roll(config)# r4-roll(config)# router bgp r4-roll(config-router)# address-family ipv6 unicast r4-roll(config-router-af)# neighbor 2001:0DB8:0:AAAA::1 capability orf Advertise ORF capability to the peer r4-roll(config-router-af)#
I think we don't need it in new xml style T2387