Yup. In the Mac OS security settings window, for "Allow apps downloaded from:", you can only choose "App Store" or "App Store and identified developers". The workflow is now:
1. Try to open the application. Get a window that says "APPLICATION can’t be opened because it is from an unidentified developer.", and below that, in a smaller and non-bold font, "Your security preferences allow installation of only apps from the App Store and identified developers." The window only has an "OK" button. (There is also a small "?" button in the lower left, which is present in lots of notification windows and presumably points to a generic help page.)
2. Open Security & Privacy in System Preferences. There is now, magically, a line in it saying "APPLICATION was blocked from opening because it is not from an identified developer", and an "Open Anyway" button.
I only discovered that workaround by accident. Before that, I believed that Mac OS had completely removed the option to run such applications. (As I recall, back when "Allow apps downloaded from: Anywhere" existed, if you did choose it, it would show some kind of warning and also revert itself after 30 days; it seemed obvious they wanted to remove the option entirely.)
I'm tempted to bring out the word "gaslighting" to describe this. Because that line about "Your security preferences allow ..." is in a context where it should be an explanation of why "APPLICATION can't be opened because it is from an unidentified developer", yet your security preferences about apps have only two choices and neither one would permit opening the application; and because a System Preferences pane now shows different options depending on what unrelated user applications you've opened recently, which is insane.
... Turns out there is a second, faster workaround. Right-click (or control-click) on the application, and click "Open". Then, instead of getting the liar window with only the "OK" button, you get a window that has an "Open Anyway" button. This workaround is, in fact, documented in the generic help page that the liar window's "?" button points to. This is also insane because it makes "Open" in its different forms (double-click, command-O, command-line "open", and the right-click "Open" option) no longer a single, uniform operation.
1. Try to open the application. Get a window that says "APPLICATION can’t be opened because it is from an unidentified developer.", and below that, in a smaller and non-bold font, "Your security preferences allow installation of only apps from the App Store and identified developers." The window only has an "OK" button. (There is also a small "?" button in the lower left, which is present in lots of notification windows and presumably points to a generic help page.)
2. Open Security & Privacy in System Preferences. There is now, magically, a line in it saying "APPLICATION was blocked from opening because it is not from an identified developer", and an "Open Anyway" button.
I only discovered that workaround by accident. Before that, I believed that Mac OS had completely removed the option to run such applications. (As I recall, back when "Allow apps downloaded from: Anywhere" existed, if you did choose it, it would show some kind of warning and also revert itself after 30 days; it seemed obvious they wanted to remove the option entirely.)
I'm tempted to bring out the word "gaslighting" to describe this. Because that line about "Your security preferences allow ..." is in a context where it should be an explanation of why "APPLICATION can't be opened because it is from an unidentified developer", yet your security preferences about apps have only two choices and neither one would permit opening the application; and because a System Preferences pane now shows different options depending on what unrelated user applications you've opened recently, which is insane.
... Turns out there is a second, faster workaround. Right-click (or control-click) on the application, and click "Open". Then, instead of getting the liar window with only the "OK" button, you get a window that has an "Open Anyway" button. This workaround is, in fact, documented in the generic help page that the liar window's "?" button points to. This is also insane because it makes "Open" in its different forms (double-click, command-O, command-line "open", and the right-click "Open" option) no longer a single, uniform operation.