You are not wrong. However x86 is dead to me for having a BIOS level backdoor built in that you can't get rid of (probably; yes I know about ME Cleaner). Not to mention Intel sat on their laurels for years. ARM are far from perfect, but maybe some competition gets things progressing again.
You asked about mini-PCs, which I don't have, however just for comparison I can say I have ODROID-XU4 + cubietruck here running and only drawing about 2W total between both of them.
I wouldn't necessarily recommend those (especially the cubietruck) these days, but there are lots of Single Board Computers (SBC) out there besides RPi.[0]
Any old desktop from a garage sale (if you can find one). People are practically giving them away these days, everyone wants tablets/phones now. We scored a quite decent one, complete with monitor, mouse, keyboard, etc. for like $25 (IIRC)!
In fairness, that was a few years ago, but I am sure there are deals to be had if you look around.
I would not recommend ARM/SBC for "first GNU/Linux computer" necessarily, you will likely have an easier time on x86, as much as I hate to say it.
It's not just them, the majority of SBC manufacturers are on these bizarre old Linux forks that have been patched all to hell and will never see mainline. Kind of same situation with most smartphones, too (as they are all the same SoCs).
There are some very noble projects (like PostmarketOS for phones, and Armbian for SBC) who try to be "mainline first" to keep these fascinating little devices going longer (and more reliably). They do an amazing job considering what they have to work with, but these are not big companies with a lot of resources behind them, so if you care about this sort of thing (not you specifically, that's for anyone reading) then consider perhaps lending a hand (or a few bucks)!
I am glad to see a growing chorus of people voicing similar concerns, which myself and others have long held. The article links to a similar article from Drew DeVault for instance (down at the bottom).
Perhaps if nothing changes after a while, it might become time to add your voice to the other public pleas. Or maybe speak to PINE64 directly/privately (I don't know how well you know them).