Thanks, Generix. I removed nomodeset, and am able to run nvidia-settings as expected.
The reason I added nomodeset is display flashing that makes the laptop display unusable when nomodeset is not present. Of course I understand now that Optimus requires mode setting.
What are my options for figuring out (ideally fixing) why the display flashing is happening?
Edit: as a workaround, I could boot with nomodeset when using the laptop display, and boot without when using the external display. Not ideal, but I could live with it.
Edit 2: issue with primary laptop display solved by adding i915.edp_vswing=2 acpi=force to GRUB_CMDLINE_LINUX_DEFAULT: GRUB_CMDLINE_LINUX_DEFAULT=“quiet splash i915.edp_vswing=2 acpi=force”
As solved the issue in this post: Built-in display glitches, HDMI external display is fine on Ubuntu 19.10 with GTX 1650
I should have known – identical hardware, OS, and symptoms.
Thanks so much for your help, Generix.