My phone is now syncing to a onedrive account based on my Google email. I already have a Office365 Home account that has 1TB storage. I cannot seem to be able to change the account sync is using. How can I do this?
Just guessing but try using the same email address for both Samsung.com and the 1TB Onedrive account. I would delete the free one drive from my phone and you may need to use a different email address than what you have for Samsung and free Onedrive.
Alternatively you can try adding that 1TB account and just sync the photos leaving the free account for the other stuff, contacts etc.
Galaxy S21 Ultra 512g(VZW), Galaxy Book (original, VZW), Tab S4, Galaxy Watch3 (VZW)