Microsoft has been building up the PDF reader in the new Chromium-based Edge to match the one in the old Edge, and today a new feature showed up in Edge Canary last seen in the old version 2 years ago.
Edge Canary build 88.0.688.0 has added two-pane side by side PDF view, helpful given that most screens are wider than they are tall.
The feature can be activated by toggling the “Enable two page view for PDF” flag in Chrome://flags.
This produces a new button in the PDF reader on restart, which lets you chose single page view, two-page view, or a mode which keeps the Cover Page visible.
All going well, the feature should show up for mainstream views in around two months.
Thanks, Leo Varela for the tip.