I want to build a PC with my son.  Or rather, at some point have it so he gets to build it (I'm thinking of torturing him by re-formatting Linux every so often and having him reinstall it).  I'd like to do with it mini-ITX for a number of reasons, one of which is that he could take it over to his mom's on alternate weeks.

I have build PCs from scratch before, but a long time ago, on full size desktops.  I'm also fairly comfortable with Linux installs.

Here are some criteria/considerations for me:

1. Relatively cheap to start out with, but room to improve or swap components.

2. based on Linux, so hardware needs to support it.  Don't want really spiffy feature set that needs Windows drivers to work.  Related to that - a mobo/chipset that doesn't require extreme UEFI mangling before it will boot from a Linux boot USB.

3. gaming?  Light gaming, possibly via Steam and possibly output to a 1080p TV via HDMI (1.3?).  I also have big gaming monitor.  But first we need to get working.

4. I'd prefer a motherboard with some basic onboard GPU, but allowing me to add a better discrete GPU later on (that's related to #1 and #3).

5. Still relatively small, because he should be able to take the box itself, minus peripherals, with him to his mom.

6. AMD?  Even before the recent security mess, I was thinking of them, just because I like them.  But I think I saw people being concerned about the quality/cost of AMD Ryzen minit-ITX boards.

7. High speed support for external HDDs (offline backups) - USB3 or eSata.

8. low power, relatively silent, even if that clashes a bit with the (light) gaming.


9. Finally, quality, quality, quality, rather than just features.  I'd never recommend ACER over ASUS in laptops for example, that's just my own personal prejudices.

10. Peripherals.  What about a console-style controller or wireless mouse and keyboards, esp if it's being used with the TV.  Anything to be careful about?

Share some pointers or war stories?  I'm not so much asking for detailed parts list as general considerations of what to look out for from people who've done this.