while attempting to take the idea found here: https://forum.openwrt.org/t/ultimate-sqm-settings-layer-cake-dscp-marks-new-script/53209

i created rules like
proto udp dport 53 mod dscp dscp-class CS5 ACCEPT;

but this creates a target of accept when looking at the iptables -L output
I find only using a target of DSCP does it function correctly
an example line that works for me looks like
iptables -t mangle -A dscpmarking -p udp --dport 53 -j DSCP --set-dscp-class CS5

so I'm unsure if the documentation is lacking enough that I'm confused how to use it or that something is broken in ferm related to dscp support.