Sorry for the late reply. It sounds like this was caused by a chrome bug? The described behavior seems like it was unable to get the OPML that was copied to the clipboard, and ended up parsing from the HTML instead.
The issue is (was) with the pasting. It works well if I copy from the old chrome to the most recent chrome. But fails if I copy from the new chrome to the old. Or from the old to the old. So the copy side is fine, the paste side is not.
How odd that Linux chrome had the problem, considering that the chromium developers are mainly on Google’s Debian desktops. And you’d think they’d have a build test bot in the cloud that would have spotted such a simple bug.