he's not currently accepting any paid fanbox subscribers or anything like that, but you can support mofu by buying his older games.
https://www.dlsite.com/maniax/circle/profile/=/maker_id/RG07898.html/
https://www.dmm.co.jp/dc/doujin/-/list/=/article=maker/id=74052/
he also has a subscribestar that might be active in the future. no paid support, but it's free to follow. same for his fanbox.