Instructions for OpenResolv?

Linux distros without systemD don't have any obvious recommendations on the nextdns setup page. The top recommendation is editing /etc/systemd/resolved.conf. For OpenResolv users /etc/resolvconf.conf is what exists. However, there is no mention of TLS in OpenResolv man page, so I don't see how I'd convert the "DNSOverTLS=yes" instruction. Has anyone figured out how to make it work? This blogger had some issues with NetworkManager and NextDNS - is there a known conflict or recommendation on their interaction?
https://yeri.be/nextdns-and-networkmanager/

For "/etc/NetworkManager/conf.d/nextdns.conf" exists, but my installation of NextDNS does not have that. Any info about nextdns conf files for use with networkmanager?

Thanks!