The author just discontinued these. Seems he/she reached out to NextDNS about working together to improve performance and enhance future capabilities, and NextDNS didn't seem to be receptive. It's a shame. This addressed some of the nagging administrative issues that have had me looking at ControlD, RethinkDNS, and others even though I've been a paid NextDNS user for several years.Apologies if this has been mentioned before, but this is news to me. Apparently there is a firefox plugin that gives NextDNS a lot of the abilities I liked about ControlD. With it you can import large lists, export configs, sort lists, and highlight domains in lists. But the ability to import lists was a huge plus for controlD over NextDNS. Not anymore!
See the addon, or tampermonkey script.