My first couple Lists were done on Listr.lol but now I really love nostrudel.ninja because I can do everything Listr does, but right from my web client. Can go to a person's profile and add them to a list and remove them from others, to hone your Lists nice.

The rss links I have to search for to find valid ones, and then plug those into https://rsslay.nostr.moe and it will spit out a PubKey to follow, and rsslay populates the feed from there automatically

Oh, and after that - the lists will automatically show up in Amethyst and some other Clients - so you can switch back and forth different lists. I currently have Followers,Mute,Bots,MSM RSS Feeds, and GR Bitcoiners(my Michigan peeps)