I bought one of these mini PCs (Beelink SER5) a while back to use as a low power desktop and the first thing I did was nuke the default partitions and install Linux. Never trust preinstalled OS.
It's probably not malware, but I was surprised to see an Asus software installer pop up in Windows last time I built a PC. Apparently it's in the motherboard firmware, but I think they at least offer an option to disable it. And it was visible, but I still don't like it.