I’m currently using a refurb sub-400 Eur laptop (R5 3500U) I’ve bought in Poland as my daily driver portable machine, which I’ve done a good number of DIY upgrades to it: for example, even if the motherboard had a SATA Slimline port, it was completey unused (probably as a carry over from an older design) and the case had no accomodation an optical drive (the space normally reserved for an ODD was filled up with plastic reinforcements), yet I’ve managed to find a way to free up some space and use the PCB of a Slimline to full size SATA to install a SATA SSD I’ve had lying around from a dismissed computer.
Also, a few years ago I’ve built a very cheap hackintosh out of a Dell Optiplex 755 for my family, who was unsure whether to keep using PCs or switch to Macs at the time. The PC used a LGA 771 to 775 modded quad core Xeon x3363 as a CPU, a Nvidia GT 210 “GPU” (in quotes because we all know just how underpowered it was, but I’ve been able to get it essentially for free and I was only looking forward to use it as a display adapter as the onboard graphics was completely unsupported by macOS and that PC had no HDMI out otherwise anyway) and a DIY’d USB DAC salvaged from a broken pair of headphones a friend of mine was throwing away as its speaker out (all I did was desolder the headphones from it and solder a 3.5mm jack in their place - macOS had serious audio quality issues with the onboard audio on that chipset, so using a USB DAC instead was highly recommended). The final build was running High Sierra, which was a few releases behind at the time as Big Sur had just been announced, but it was surprisingly usable especially considering all the DYIng and how some of the components had 10+ years on their back!
Approved!