@mejofi OFC, if that's a hard thing consider some thing like a professiomal prebuild.by a reputable systems integrator like #ThomasKrenn which they offer with #FrontIO and #OPNsense compatibility as well as #LongtermSupport and #SpareParts.
https://www.thomas-krenn.com/en/

For #redundancy via #CARP just choose two identical nodes and have them connect directly to each other via a dedicaded NIC/Port using a patch- or direct-attach-cable...