As
@64K mentioned this could easily turn into a build-this-thing type thread. I say all the part picker posts should give you a rough idea of what to look for if youre wanting prebuilt. Just keep in mind as another person mentioned, prebuilts do tend to come with single channel single stick of ram and a not up to spec PSU. As far as AM4, I wouldn't invest into it even if it was a 5700x3d nor Intel 11th gen or older, just not going to get your moneys worth out of it.
The only prebuilts worth buying are simple office/media centre PCs, certain types of workstation from professional services, laptops, or from system integrators that simply assemble parts of your own choice.
The premium for what is in essence a one hour put the lego pieces together job, is quite severe, especially for those on a limited budget.
Of course, there are higher level optimizations and component choice/assembly tweaks that can improve the end result, but ultimately assembling a PC is incredibly simple. Parts have their own warranties which are often longer than those given grudgingly and often for a premium from system integrators too.
SFF PCs, or custom watercooling is another matter, but those are challenges for the initiated.