Thanks so much! My particular machine (Optiplex 7050) has a very finicky mobo, which specifically does not allow simultaneous use of integrated graphics and dedicated graphics card. I didn't know about this limitation when I bought them, but I can live with it. After working around the driver issues, it's a nice enough machine.
Given my last write-up, I thought I should provide an update about the power of the cheap graphics card with a Win 8.1 driver.
I just discovered that the Win 10 bootloader is not necessarily needed to get Win 7 to UEFI + Secure Boot without using UEFISeven.
I had another of the same hardware (Opti 7050) where I previously installed Win 7, via dvd, in MBR. So I ran mbr2gpt, and then installed the cheap graphics card with the Win 8.1 drivers.
After some fits and restarts, the system was able to run properly in Win 7 without CSM. I had previously failed to discover this feasibility, because on my previous attempt the graphics card's fits and restarts caused me to prematurely assume it would not work without an advanced bootloader. Today, I had less caffeine, so I let the machine do its thing until it had enough time to get the graphics working without CSM.
In particular, on my first start-up without CSM under the new graphics card, the system seemed to be hung for a long time, with frozen graphics, although extensive disk activity was occurring. After a lengthy wait, the machine re-started itself, and since then it's been working just fine without CSM, and no graphics glitches.
After Win 7 was working with the graphics card, and without CSM, I added the post-2019 updates via Simplix, and now it secure-boots reliably.