i had the same issue as you. i used mixamo, uploaded my character and had the auto-rigger do its magic. then i imported it into unreal engine and through skeleton re-targeting i was able to get my guy using all the anim starter pack animations. i did this all for free, except for the character.
it works really well with small inconsistencies depending on how much time you spend on re-targeting.
check this out
it seems overwhelming at first, but i’m a total newb and got it working, i believe you will do fine.