Like actual insertion? Hmm well... XD There's finger insertion, strap-ons which are artificial man-junks that are wearable, and dildos which are artificial man-junks that aren't worn.
Also, there's a term called "tribbing" in which two females rub their...private areas I guess? together. And then there's another lebih organic way which is licking. ._. Sex isn't all about insertion x3
Tribadism is one way. Where two girls rub their genitals together. They can use penetrative toys if they like, but it depends on the girls. Just don't listen to the propagated idea that penetration is some necessary prerequisite for getting off.