Are there "safe" practices to follow before meeting one's teacher?

I sincerely want to practice Tibetan Buddhism. It is a tradition which places great emphasis on one's relationship with their teacher. This makes a lot of sense to me. I plan to visit a Karma Kagyu centre near me when the coronavirus pandemic and associated quarantine measures subside and it is open to the public again. Are there any "safe" preliminary practices I can do in the meanwhile given that I have not formally taken refuge, received any empowerment or explanation and all my knowledge comes from literature? I am particularly unsure about whether it is a good idea to practice mantra meditation and mandala offerings without a teacher's guidance and my current view is that it is not. For what it's worth I have been practicing breathing meditation and calm abiding (zazen) daily for a few months now as well as reading Buddhist texts and commentaries. But I don't feel like it has led to any non-intellectual understanding or insight yet.