It’s generally easier because the drivers are built in. Nvidia is perfectly usable, but it’s more susceptible to breaking during kernel updates. It’s not as bad as everyone makes it sound though. That said, AMD is usually the way to go on Linux unless your use case requires Nvidia.

I also switched to AMD+AMD. The GPU support being better on AMD comes from the Open Source driver that is integrated into Linux. But there are caveats. In example if you need OpenCL or other features, it can be problematic with AMD. Plus, if you have a Nvidia card 20xx series or newer, then you can use the new Open Source driver too. And Nvidia support for Wayland and other stuff got better nowadays (just reading about it, no personal experience with current, my last Nvidia card is 1070).

While I prefer AMD gpu now, the "better support" is not really black and white.

With old hardware, beggars can't be choosers. I get the appeal of the nouveau driver, but if your goal is to save a machine from the landfill, it's probably the better compromise to use the proprietary driver and keep it actually competitive for as long as possible. Those 900/1000 series cards are still plenty powerful today, even if they can't quite do AAA gaming anymore.

Not exactly. There are two alternatives, depending on which card you have: a) the proprietary driver, b) the new Open Source driver that supports RTX 20xx series and upwards.