I am experiencing significant screen corruption on an old Acer Aspire 9300 laptop, equipped with the GeForce Go 7300 graphics chipset w/128MB of RAM. When Xorg is started by gdm, the screen is covered in artifacts that obscure most, if not all, of the widgets and window contents displayed on the screen. The screen corruption is present on the GDM login screen and on the default Ubuntu desktop. Moving the window around causes tearing, screen artifacts, additional widget corruption, and other nasty artifacts that render the desktop unusable. This behavior is reproducible with Wayland enabled or disabled in /etc/gdm3/custom.conf, and is reproducible using Ubuntu 20.04's 5.4 vendor kernel.

EDIT: When I add 'nomodeset' to /etc/default/grub and update the bootloader, the graphics load properly using the Ubuntu vendor kernel's framebuffer drivers with no artifacts, screen tearing or other corruption.

I've checked the dmesg and verified that the nouveau driver has properly detected the chipset and appears to be enabling and executing KMS correctly. I don't want to use the proprietary nVidia driver and I don't want to permanently disable KMS on the kernel command line either. I am in the process of compiling a mainline 5.10 stable kernel to see if its copy of the nouveau driver fares any differently.

Has anyone experienced this type of corruption with the GeForce Go 7300 on an Acer laptop?

I recommend a slightly more conservative distro with an eye on old hardware, like antiX.

You might benefit from the nvidia proprietary driver.
Find your model here and see what drivers are available/required.