[bizarref00l]

Not sure if mini-itx fits your taste but epyc 3000 may be an option. https://www.servethehome.com/supermicro-m11sdv-8ct-ln4f-revi...

[officialchicken]

M-itx cases are about 7.5 liters at the smallest (XBox size) although some specialty cases exist in the 5-6 liter range; a NUC is typically about 1 liter.

[kllrnohj]

Those cases tend to have full-size GPU support. You can find smaller cases for APU usages, like this one: https://www.supermicro.com/products/chassis/Mini-ITX/101/SC1...

But you can also find Mini-STX boards like this one: https://www.sapphiretech.com/en/commercial/amd-fs-fp5v which should then fit in something like this: https://www.silverstonetek.com/product.php?pid=708&area=en

You can also find some very small Mini-ITX cases on things like aliexpress: https://www.aliexpress.com/item/32994653418.html?spm=2114.se...