Dual-monitor setup: broken icon placement and other oddities

I'm running Zorin 15.3 Pro. I have a dual-monitor setup. I have three issues that I cannot resolve.

  1. Regardless of how I configure my screens in Settings or physically wire them, my login prompt is always presented on the 2nd (non-primary) monitor ... which is in portrait mode.
  2. Post-boot login, all desktop icons are "scrambled." They are in three or four groupings of overlapping clumps. No matter how I rearrange them or use "Organize Desktop by Name" and "Keep Algined, " they do not stay organized or aligned across boots.
  3. When I launch an app - any app - there's a great chance it will open on the display where it was not used prior to its last use, e.g. I'll use Firefox for hours on my main (primary) monitor - opening, closing, quitting; I'll quit FF, walk away for a few hours, come back, open it, and it's not uncommon for it to open on the 2nd monitor.

None of these issues are deal-breakers. They've happened since "day one" of my OS install. I'm on a totally different video subsystem than when I first installed Zorin - I upgraded from a Radeon WX3100 Pro to NVIDIA 1650. Both monitors are identical make/model (LG) running at the same refresh frequency (60Hz) with identical resolution (1920,1080). One monitor (primary) is landscape, the other (secondary) is set up as portrait.

Any ideals what I might try to resolve these issues?

This is a really old posting about Ubuntu 12.04! But who knows, the solution might work - no guarantees!:

https://itectec.com/ubuntu/ubuntu-dual-monitor-configuration-with-one-in-landscape-mode-and-the-other-in-portrait-mode/