“isnt there something about an eved canaani who is owned in partnership and one partner gives him freedom and he has a bris, etc. ?”
An Eved Canaani is in fact a sort of half-Jew, as he is chiyev in some commandments. He can’t marry a Jew unless he is freed. IIRC, in the case of an EC who is owned by more than one Jew, and for whom one of the Jewish owners has freed the EC from that part-owner’s bondage, we force the other Jewish owners to complete the liberation from bondage.
After freedom, EC becomes a full fledged convert, with no need for a beit din, and no need for formal acceptance of the mitzvot. I have seen some suggest that this is a way around the current “conversion controversy”.