Homeland Security’s two-page terrorism bulletin dated today is linked here:

https://www.dhs.gov/sites/default/files/ntas/alerts/22_1130_S1_NTAS-Bulletin-508.pdf

It gives no specifics of what constitutes an act of domestic terrorism related to the Nov. 8th election.

Has Congress given Homeland Security authority to arrest anyone for any reason?

The House already passed a bill that will do that.

It is called HR 350.

https://www.brassballs.blog/home/hr-350-fbi-to-have-unlimited-money-to-arrest-anyone-for-anything-any-time

Fusion Centers will detain those people who are arrested.

Locations were updated today by Homeland Security:

https://www.dhs.gov/fusion-center-locations-and-contact-information