It's awesome that they have a colleague like you to help them and champion it! One of the things that helped me learn a ton about Teams very quickly was having a colleague who was curious and willing to test things and try things in teams as we discovered them.
So call them on teams regularly and show off what you know! Blur your background - or soon, set your background to something fun! Share something on your screen, or conference in someone else.
A combination of useful and fun is great for change management.