LC has had no issues at all for me until the 10.1 update. Now, it doesn't behave correctly at all on two monitors.
I'm on an iMac Pro 2017 and have an Apple LED monitor as my second screen. Nothing related to the second monitor works properly anymore.
I set LC 10.1 Preferences > Display to use the Apple LED display as the second monitor. This preference was erased after upgrading to 10.1 and had to be set again. When I click the "2" button to display a normal loupe (full image) on the 2nd monitor, it appears on the primary (iMac Pro) monitor in a window labeled "secondary display" at the top. If I drag it to my second monitor, as soon as I click on anything, it bounces back to the primary monitor.
If I go to LC Window > Move to LED Cinema Display - the main window just stays on the primary display.
While editing in Book mode today for a Blurb book, every time I accidentally clicked on the LED Cinema, the primary interface moved to that monitor. Then, Window > Move to Built in Retina Display did nothing. The only way to get back to the primary display was to Quit and re-launch. This happened half a dozen times, but now I cannot reproduce.
Bottom line - LC 10.1 will not use the 2nd monitor at all, even though it knows its there. Worked perfectly for all released up through this one.
Ideas? Preferences or something, or is this a bug in 10.1?
Lightroom Classic version: 10.1 [ 202012012023-e92d50bb ] License: Creative Cloud Language setting: en-US Operating system: Mac OS 10 Version: 10.15.7 [19H114] Application architecture: x64 Logical processor count: 20 Processor speed: 3.0 GHz SqLite Version: 3.30.1 Built-in memory: 65,536.0 MB Real memory available to Lightroom: 65,536.0 MB Real memory used by Lightroom: 6,315.9 MB (9.6%) Virtual memory used by Lightroom: 16,395.6 MB Memory cache size: 1,354.1MB Internal Camera Raw version: 13.1 [ 658 ] Maximum thread count used by Camera Raw: 5 Camera Raw SIMD optimization: SSE2,AVX,AVX2 Camera Raw virtual memory: 250MB / 32767MB (0%) Camera Raw real memory: 262MB / 65536MB (0%) Displays: 1) 5120x2880, 2) 1920x1200
Graphics Processor Info: Metal: AMD Radeon Pro Vega 64
PS. Every time I re-launch LC 10.2, the Preferences > Display is reset to the primary monitor with an obvious red error message "Lightroom is already open on this monitor. Please select another monitor." The selection of the second monitor just doesn't "stick", much less work at all ever anymore.