How the lists are picked
We look for posts in the last month that are a real question: what tool, what alternative, how do you handle this workflow. A sub that is mostly memes, job ads, or launch posts from other founders does not make the list, even if it has a million members.
Start with one niche. Read the rules. Comment for a week. Then add a second. The SaaS founders page is the one most software companies should open first, and then leave if their buyer is not a founder.
Subscriber count is the wrong sort. A sub with two million people and one tool question a month will not send you a customer. A sub with forty thousand people and a tool question every morning will. The lists name both the room and the kind of post inside it.
Why this is not a directory of every sub
A directory of hundreds of subs looks complete and sends you nowhere. This library starts with the rooms where a software buyer asks for a tool, and it says which famous rooms to skip in week one. Subscriber count is the wrong sort. Posts per week that are a real question is the number. The SaaS founders page is the worked example. If your buyer is not a founder, use it to learn the pattern and then leave.