BlueFriday
https://app.bluefriday.uk/ The nichest of niche social network clients. It's for people in one particular country, who watch one particular TV program, on one particular day of the week. Now that the cost of writing software is zero, I love that my focus have moved from vain attempts to generate passive income to just building whatever random shit I feel like. Wish I'd made that choice earlier in life, but no worries!