@wkeller --I hate to ask people if they can upgrade but can you upgrade the opevpn client you're using? This post https://community.openvpn.net/openvpn/ticket/849 is referencing 2.3.12. My example above is using 2.4.9. It looks like you're using 2.3.4. I've a feeling either pull-filter or those specific pull-filter references weren't adopted until at least 2.3.12.
@kevink00 I know that my DD-WRT and the OpenVPN that it comes with are quite dated and in need of an update. I've been planning a move from DD-WRT to opnsense. Till then I will likely have to forego VPN.
The OpenVPN on DD-WRT appears to be stripped down a bunch, so even some of the documented options do not actually work. (as an example, no mater what I do, I can not change the --mute setting to anything other then 6).