I haven't tried to make vegan panna cotta. However, you can certainly substitute with non-dairy ingredients to make this dairy free. You could also make panna cotta with agar agar by substituting the gelatin for an equal amount of agar agar powder (not flakes). Please note that agar agar does need to be boiled to activate its gelling properties. Also please note that I haven't personally tested this substitution. So for best results, I recommend following a vegan panna cotta recipe so you know it'll work.