I have introduced several different types of food to my 20 weeks old baby boy like puréed fruit and baby biscuit.
I broke the farley’s rusks biscuit into half and let my baby hold it in his mouth. Since he is teething at the moment, he likes to bite onto his toys so the biscuit is perfect as his saliva soften the biscuit edge and he swallow the little moist crumbles. However, do supervise your baby at all times when they are eating because they might choke on a big crump of biscuit.
I also mashed the remaining biscuit and mixed them with his leftover milk. He loves it mixed with banana purée too.