Dealing with drm drivers taking a long time to load/probe, enable use-simpledrm by default?

Recently there have been a number of Fedora bug reports (bug 2183743, bug 2276698, bug 2283839, bug 2312355) about the plymouth boot splash not showing properly on PCs using AMD GPUs.

The problem with plymouth and AMD GPUs is that the amdgpu driver is a pretty big driver, which easily takes up to 10 seconds to load on older PCs. The delay caused by this may cause plymouth to timeout while waiting for the GPU to be initialized, causing it to fallback to the 3 dot text-mode boot splash.

I wrote a blogpost about this documenting 2 workarounds (depending on the systems' config): https://hansdegoede.dreamwidth.org/28552.html

I'm filing this plymouth issue to track getting this fixed without requiring users to have to apply these workarounds.

One option, which was also discussed in #110 to resolve that issue is to make the "plymouth,use-simpledrm" kernel commandline option something which is also configurable from the plymouth config file and changing its default to true.