Initially asked in forum https://forum.vyos.io/t/vrrpv3-supportability-and-questions/11318
keepalived which is used by VyOS defaults to VRRPv2 when IPv4 is used and VRRPv3 when IPv6 is used.
There is no way to manually force VRRPv3 for IPv4 addresses.
This feature should be added.