So over the years I have run Linux on everything from a Pentium 2 300Mhz Desk top PC with 192Mb of RAM, all the way to my 5year old i7 Tower with 24Gb Ram, and much in between. My current lowest spec unit is a 2008 Acer Aspire One with an 8Gb SSD and 1.5Gb Ram the SSD is the one soldered to the mother board so not up gradable but you can boot from USB so it’s possible to install from and to a USB flash drive as the primary HDD, turning the internal SSD into storage. as those early netbook SSD’s were so slow it runs a little faster from a modern USB3 than the original drive despite the slow USB interface which I think is 1.1 although you need a 32bit OS as despite the atom 1.6Ghz CPU being a single core HT processor it was not 64bit.
I have recently run both 32Bit versions of Peppermint and MX on this PC and while it will not break any speed records it does still run and if it had a battery that held a charge would be an OK portable for the kids to take to school. It does however weigh more than my i5 Toshiba Z30 with exponentially more power and storage
My Lenovo X61s is a more practical Laptop of a slightly older vintage, but it has a core2 duo running at the same 1.6Ghz 4Gb Ram and a 120Gb 2.5" SSD and will run a wider selection of Linux Distro’s and is about as portable as the Acer.
Other than that my current stable include:
Lenovo X200 tablet, X201, X230i
Raspberry Pi’s of various flavors including the latest 4B 4Gb model
and an old mac book 2007 (the rarer Black one) that I’m still trying to figure out how to get Linux on it.
PS correction, I said the Acer is the lowest spec PC I currently own but that’s not true, as I still have an original Pi B with 256Mb Ram and only 2 USB ports.