Hi Corey Doty,
As per the Docs article below, the background blur feature requires a CPU with AVX2 support:
https://docs.microsoft.com/en-us/microsoftteams/hardware-requirements-for-the-teams-app
Engineering has confirmed that a crashing bug was identified recently on machines without AVX2 which is why the feature was available previously for you and is no longer showing up. The bug has now been fixed and will be rolling out in an update soon. Once that fix reaches your machine, the background blur option should appear again.
Thanks,
Omar