After one year of running a 5e Birthright campaign, I have collected bits and pieces from a lot of 5e Birthright conversions and would like to post my houserules as a whole here.

For realm management we are using the 2e Rules and for Mass Battles the excellent 3.0 edition conversion.

I want to give thanks to Marsupialmancer, callinostros, Morten Helles, zcthu3 and Duck Call Lass for their effords and inspiration.