Hi @joe.hiko ,
We managed to put Python 3.9.9 in TorizonCore 5.7.0 with a custom layer using Yocto. You can take a look here: Upgrade python version in TorizonCore with yocto - #7 by lucas_a.tx.
You can disregard the changes I suggested in my previous answers, use a clean TorizonCore Yocto build and follow the instruction in the link above.
See if this helps you.
Best regards,
Lucas Akira