It seems there is currently a bug in FRR that causes issues when trying to enable BGP EVPN in a different VRF than the default one.
There is however a workaround for this, if you first add the router bgp 1 vrf stuff statement to the config and then router bgp 1 it should actually work, the FRR bug has to do with the order in which they get configured.
If you first define router bgp 1 and then router bgp 1 vrf stuff (which is what VyOS does) then you get a Please unconfigure EVPN in VRF (null) error.
The FRR developers are working on a solution (there is no issue on GitHub yet as far as I know) however this might take a while to get released.
Update: I opened https://github.com/FRRouting/frr/issues/9405 for the FRR issue.