Mac mini M2 (2023)  An M2 Mac mini - I think I have the Apple (non)capitalizations correct - was too good to resist. "Only" an M2 chip rather than an M2 Pro in this one, but that is plenty fast enough for me.

RPi 400  An ARM chip inside a glorified keyboard connected up to everything else via lots of wires for less than a hundred quid - is this 1980? Odd that the mouse appears to be set up for left-handers.

RPi 4B  The ARM chip without the keyboard (or anything else).  Raspberry Pi OS helpfully contains a free copy of Mathematica. Raspberry Pi OS 64bit is now available to speed things up a little bit.

MacBook Air M1 (2020)  Now with a sensible keyboard and ARM innards. The M1 chip is fast and the x86 emulation via Rosetta2 "just works" for everything I need. Also, to a good first approximation, the battery life is infinite. An annoyance is that attaching more than one external monitor requires DisplayLink chicanery and is inherently flaky.

MacBook (2015) Featherweight, if a bit light on ports. Officially orphaned by macOS 12 Monterey, but OCLP saved the day.

Dell XPS-13   (9370  and 9305 versions) The 9370 is from a few iterations back but it still makes a handy Ubuntu/Windows laptop, albeit with a very unflattering webcam angle from the bottom of the screen. The 9305 is more recent, essentially transplanting newer 9310 innards into the now old-style chassis of the 9370 and similar, though it manages to put the webcam above the screen.  

MacBook Air 11"  Back from the dead with ChromeOS Flex to make a very nice ChromeBook. Everything works except the webcam.

IdeaPad Duet 5  Big brother to IdeaPad Duet 3  Chromebook below.  It has almost the same innards,  but sports a larger (16:9, 1920 x 1080, 13.3-inch OLED) screen.   Curiously, the stylus technology is still USI (not 2) on this one as the pixel density is lower.

IdeaPad Duet 3  The second iteration of the IdeaPad Duet Chromebook. It is slightly bigger (5:3, 2000 x 1200, 11-inch screen) and quite a bit faster c/o a Snapdragon 7c Gen2 CPU than its predecessor.   It seems the orginal USI didn't quite cut it, this now has USI 2: Universal Stylus Initiative 2, one stylus to rule them all. 

iPad Mini (2021) Out with the Lightning port, in with USB-C. In the usual Apple style you have to buy a new Apple Pencil 2 to work with this one. 

iPad Air (2020) See above.....

Xiaomi Poco F3  More like the orginal Poco F1 than the F2 Pro so it offers performance at a very keen price, especially when bought at a discount.

OnePlus Nord   "Pretty much everything you could ask for"  according to the advertising blurb, which is pretty much correct.