Update: Aug 9
The Wall Street Journal offers an op-ed by Clint Watts as a Saturday essay on how to fight specifically bottom-up domestic terrorism. It notes that extremists have been driven into corners by major social media.
Update: Aug 12
From USA Today, here is an op-ed by R. Derek Black, "This is how white nationalists think about shootings", p 5A in the print edition (I bough it today), tricky URL. However the deplatformings and payment processor cutoffs he supports have ensnared people who are not white nationalists by the usual meaning.