As mentioned in RFC 4451, BGP speakers often derive MED values by obtaining the IGP metric associated with reaching a given BGP NEXT_HOP within the local AS. This allows MEDs to reasonably reflect IGP topologies when advertising routes to peers.

In the huawei router equipment, when the router learns a route from an IBGP peer and advertises it to an EBGP peer,

apply cost-type internal

if the above command is configured, the router will set the MED value of the route advertised to the EBGP peer to the IGP metric value of the next hop for that route.

As for cisco router equipment, the same command is as below.

set metric-type internal

However, I can not find the same command in FRRouting (version 9.1). It could also be that I overlooked it. So, I kindly request to add this new command and function.