I read through Plutonium help page on this link https://plutonium.pw/docs/install/#i-just-want-to-update--i-already-have-bo1-installed.
It suggests using torrent software to install the DLCs so that a person can play all DLC maps through Plutonium. This is the link provided on Plutonium https://www.fosshub.com/qBittorrent.html.
I have not used the link above at this time however.