The show ip route command should support more commands, like FRR does from vtysh terminal.
Example:
vyos@vyos-gns3:~$ show ip route tag 20
Invalid command: show ip route tag [20]
vyos@vyos-gns3:~$ vtysh
Hello, this is FRRouting (version 7.0.1-20190820-04-g047efd6).
Copyright 1996-2005 Kunihiro Ishiguro, et al.
vyos-gns3# show ip route tag 20
Codes: K - kernel route, C - connected, S - static, R - RIP,
O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP,
F - PBR, f - OpenFabric,
> - selected route, * - FIB route
B>* 172.16.251.0/24 [20/0] via 172.24.1.218, tun0, 00:11:31
B>* 172.16.253.0/24 [20/0] via 172.24.1.226, tun1, 00:11:30