Sounds good. I won't host MintPress because it is explicit propaganda, and if one of the others does anything squirrely I might reserve the right to remove it, but at first glance it all seems fine.
So the ones that seem to fit the lefty_stacks vibe are: Caitlin Johnst, Socialism for All, Ken Klippenstein. I added those to lefty_stacks, although your link for Caitlin Johnst seems to be broken. Dropsite News should probably be its own thing, so I made: !dropsitenews@ibbit.at.
How about this: I can make a separate community for you, "lefty news" or something (just let me know what name you like for it), have you be a mod, and just be able to add or delete individual feeds to it as you see fit. Pretty much everything you're asking for here can go into that one community, but then if some of them are super high-traffic or sufficiently their own thing, then maybe they need to be moved to their own communities, but we can cross that bridge when we come to it, and in the meantime you can have the community and do what you want with it (again just subject to the restriction that if something is objectively dishonest I won't allow it, MintPress is the only one I'm aware of on that list that is that). How's that sound?
Penny Arcade I added, !penny_arcade@ibbit.at. Isn't there already an SMBC community somewhere though?