I have Acrobat Reader DC v2020.013.20074 running on Mac OSX v 11.1 Big Sur. Since last week I have stopped being able to digitally sign PDFs: upon opening any fillable form a received a notification window saying that "some features of Acrobat Reader would not work properly". Attempting to click a digital siganture field causes the window to flicker, as if the siganture fill window was attempting to open, but none appears. Clicking on fountain pen icon allows signing using my preloaded signature, but not the timestamped version that my employers require.
Attempting to create a signature field in a PDF no longer works either.