P: Compare View on 2nd Monitor shows no image on Zoom.

Yep, turning off use graphics processor fixes it for me too. Mine's a NVIDIA GeForce GTX 1650. Tbh, mine's not a particularly powerful graphics card and switching it off doesn't have a significant impact on performance. Which, by the way, is noticeably and significantly worse in V13 than it was in V12.

Same here.: Loupe renders a black screen on my secondary monitor when the zoom is set to 100% (with Development module on the primary monitor). Everything is fine when using  the  Library module on the primary monitor. Turning off  use graphic processor solves the black screen problem but that is somenthing I hate to do. I didn't get a nice graphics card just to disable it in LR

Last Nvidia Studio driver v 537.58 and last LR v 13.0.1, Windows 11 up to date.

Updated lightroom (13) and what the heck happened to the second monitor preview when zooming 100%? It goes black and does not redraw the image, although it's fine in the main monitor view.  This has never once happened to me in the past. I'm using RTX 3080ti wth latest studio drivers, Windows 11 Pro. I've never had this issue 

I have the same problem with second monitor after update. OK on display, black screen on zoom. W11 with NVIDIA also

The same behaviour happens in my system since the latest update (v13....). Besides that and even worse is the gamma shift on the secondary monitor. It is so pronounced that even dialing down the exposure results in a kind of  "solarized" image, instead of pitch black. I also feel that the colors are a bit off on the secondary display. Tried everything (I think) in the preferences menu, but the result was consistent, which is not acceptable.

I downgraded to version 12.5 and none of this happens anymore. No loupe/zoom problems, no gamma shifting and the colors are again coherent in both displays.

Both my screens are calibrated.

Well after starting Lightroom again today the problem is back. (After a PC restart)

Changing info view mode does not help anymore.

For me it is vice versa - I can zoom without issues in the library module but not in the develop module.

Seems to be very weird!

[EDIT]

I just downgraded to 13.0 to see if that fixes the bug for now (cannot go back further due to database was upgraded already).

The bug is also in 13.0 - so was introduced in the 13 line.

I have the same issue here on a windows 10 pro machine amd ryzen 7 with a Nvidia 3050ti grafic inbuilt. I work with 2 external Monitors and up to now had no issues with that.

I double checked that it is no regression of that old Hardware acceleration bug. The behaviour also occurs when switching off hardware acceleration.

I'm using the same config (W11 pro - 3060Ti with same studio driver)
Changing Loupe info doesn't make any difference on my system.
Develop mode + zooming in on pics on secondary display still results in black screen.

When in Compare mode on secondary both images appear but upon zooming in on the left-one the right-one will show up zoomed-in but the left-side picture disappears and viceversa.
Not great when comparing different edits on the same picture...

Have Graphics Processor switched off now though as this doesn't have any issues, though Lightroom occasionally throws you a popup to enable the Graphics Porcessor 'cause it's (supposedly) supported.

Hope they'll fix this soon.

I initially had the same issue with LR13, Win11, NVidia RTX 3060Ti with newest Studio driver 537.58

When in develop, if I changed to other zoom levels other than fit on the 2nd monitor then a portion of the screen went black.

I then noticed that the Loupe info on the 2nd screen would not change when I toggled through each mode with the "I" key.

I switched back to the Library Loupe view and toggled through Loupe info mode with the I key. (Both screens changed)

When I went back to Develop mode the 2nd screen zoom was working correctly.

But, I am still unable to change the Loupe info mode on the 2nd Screen while in Develop only the primary screen changes.

The 2nd monitor stays set on whatever was applied while in the Library Loupe.

So, it is now possible to set both monitors to show different Loupe Info modes (2nd monitor needs to be changed in the Library Loupe).

I do not believe that was previouly possible? I am sure both Develop and Library Loupe shared the same Loupe Info modes?

So, far the 2nd monitor zoom blackouts have not re-occured since changing Loupe info.

So, it looks the blackout issues with the 2nd monitor zoom are related to the Loupe info?

I have NOT reset preferences.