Well, Wattpad can be a good source. Although it mainly focuses on regular stories, there are some users who create and share interactive fiction stories for free. Also, some writing communities might have sections dedicated to sharing free interactive fiction among their members.
There are several places. One option is to look on itch.io. It has a wide range of free interactive fiction works created by indie developers. Another place could be some free e - book platforms where authors might share their interactive fiction for free to gain exposure.