Thanks for your answers, all.
I forgot to tell why I think kde is better for old people. Because, they often miss/wrong clic on panel removal mandatory items, which is difficult with kde, while it’s easy with xfce or mate. You have no idea how many times I’ve been contacted to fix that many months after Linux installed.
You can consider creating two panels - let’s say one on the left side, the other at the bottom.
Immutability
Edit ~/.config/plasma-org.kde.plasma.desktop-appletsrc
Find the text immutability
Your panels are grouped in sections, so work out which Containment corresponds to which panel, the location key is the key, then find the line:
immutability=1
If you change that to immutability=2 then THAT panel should be safe.
Be sure to create some kind of CHEAT SHEET for the desktop… I would think to set it as a desktop wallpaper - a fairly plain or patterned wallpaper with notes printed on it.
Set up backups and snapshots.
In my experience, KDE is not the bottleneck (all the DEs use pretty similar resources, give or take 300mb). Rather, the distro under it is what dictates performance, and that matters a lot. Some are slick and efficient, some are not, even with the same DE. For really minimal and 32bit hardware I would look at Puppy. But I run PCLinuxOS/KDE on a 2006 laptop (first-generation x64, 2GB RAM and spinning rust) and it’s not slick, but it’s usable. On my 2013 laptop (early i5, 4GB RAM, spinning rust), even Fedora/KDE runs well enough, and upgrading to 16GB RAM made it downright lively. Upgrade RAM whenever you can, find 'em an SSD, and pretty much any x64 system will perform adequately for basic use.
Isn’t it an important question here whether or not they’ll expect to be able to watch videos properly, in particular in the browser? That does impose a lower limit on the hardware, and for older CPUs/GPUs it may also impose an upper limit on the kernel (I’m typing this on a mid/late 2010s N3150-based notebook that can go for months with a 4.14 kernel but not with anything newer, because of the i915 kmod).
KDE Plasma4 had a reputation for being among if not the lightest “serious” DEs in terms of resources used, and I can confirm it worked really well on an Aspire One netbook (and I’m not even talking about the “netbook” set-up, though mine does have 8Gb RAM). Of course it didn’t yet use QML for just about everything.
FWIW, I’m in the process of replacing that system with a refurb HP Elitebook 820 G3 (i7 inside) that I got for about 175€. The nice thing about that model is that it can hold a 2.5" SATA drive (7mm!) plus an NVME. Just to say that upgrading hardware to something recent’ish doesn’t have to cost a lot, possibly even less than what a quality bigger SSD will cost nowadays!
Many of you are off topic. I don’t ask what distro put on old computer, because I know how to select it. My ask concern only KDE plasma 6. So, it seems to be 4 Go but I don’t understand what type of old intel.
plasma 6 will run about as well as plasma 5 on any 64 bit intel cpu, what the minimum cpu is comes down to your pain threshold for how responsive you required the desktop to be.
you can turn off animations, and kwin effects to help lighten the load.
It can also help to select the XRender backend for the compositor.
I expect that Plasma6 will run well enough on that old N3150 of mine. Probably better than a modern browser.
I’m running Fedora 43 with KDE 6.6 on two ancient laptops: an ASUS ROG G751JY (2016), and a Lenovo X380 Yoga (2018). The ASUS has:
- 32 GB of RAM
- i7-4710HQ CPU @ 2.5 gHz
The Lenovo:
- 16 GB RAM
- i5-7200U CPU @ 2.5 gHz.
The only issue I have is that there’s no decent driver for the fingerprint reader on the Lenovo… at least, not that I’ve found so far.
But, this year I’ll be breaking the old fart mold (I’m 70) by buying a new laptop (My wife said I could! Honest!) My biggest concern is finding one without that annoying Co-pilot key.
Hopefully the more Linux-oriented manufacturers like Tuxedo and Slimbook would be OK.
If they don’t put a Windows logo on the Meta key, then they hopefully won’t entertain the Copilot key.
This is possibly the single most exciting thing that I managed after buying my first mech 75% keyboard… to have that option on a laptop would be superb.
After I picked up a set of switches for a silent/tactile feel (so quieter than my previous logitechs) I then picked up a set of PBT keycaps with no Win or Logo on the Meta key.
Utterly sublime… plus the fact that after a year of heavy typing, it still looks exactly as it did when new.
What’s your definition of ancient?!
Well that is maybe ten years old, so pretty ancient I’d say.
That cpu is only dual core (4 threads), so it WAS respectable for light office work and web browsing ten years ago…
Multitasking now would pretty much get it bogged down…
Good luck finding where to plug in your nVME drive - and it’s quite likely limited to 8GB, 16GB RAM if you’re lucky.
32GB (and PCI 3.0 for an NVMe).
Of course, what you can actually plug in depends on the manufacturer. How much RAM it can handle is moot if the RAM is soldered in.
Ah, ok - so pretty impressive back in the day I guess…
My experience started with a core2duo, replaced some 7 years later with an i3-4130 to revolutionise the desktop experience having binned the old nVidia card… and that could still be chugging along even now if I didn’t have a PSU failure take out the Motherboard/cpu (not sure which, neither was worth replacing given costs and alternatives).
So now I’m on an aging Ryzen 5600G, and i can see this thing chugging along for a good while longer.
So really - depending on exactly what you regard is the ‘minimum’, I wouldn’t want to lose a basic GPU or iGPU, ignoring whatever software requirements you might have, the basic desktop experience is just so much smoother with even a basic iGPU.
A Core2duo could do the job, if you had a separate basic level graphics card (hopefully not nVidia, and hopefully supported…). With no GPU, then you’d be looking for a ‘snappy’ desktop experience with no compositing/animations/effects.
LOL, like I said in the original message: 2016. 
I’m not even that old, but my first computer came with a 25 MHz CPU and 4 MB of RAM! Amazing how far we’ve come in just a few decades, at least in terms of raw performance.
Well, that’s something we can call ancient (I had to re-read to ensure you indeed said 4Mb ;)). 10 years old is just that, old (or rather, older). And I definitely hope that there are enough people on the KDE dev team who have compatible views! (Sadly KDE inherits from Qt in this aspect… but that’s less relevant on Linux.)
My main machine until recent was an MBP8.1 with a 2nd gen mobile i7. With 16Gb of RAM it’s still fast enough for most things including the kind of multitasking I do. That 9-to-6 yo Elitebook I got is noticeably faster though and it’s still “only” got an U6500 i7.
There used to be a saying that computers became obsolete as soon as they hit the market. I’m not so certain that’s still an appropriate bit of wisdom, insofar as it ever was for the majority of home users.
Most consumer hardware topped out at a practical level of power that a normal user can make use of quite a long time ago, I’d say 10 or 15 years at least. Even graphical performance was pretty much “good enough” for incredibly immersive video games back then. Anyone here ever play the original S.T.A.L.K.E.R. or Mass Effect games from 2007? They still look awesome today. And that was 19 years ago!
The hardware gains since then have been in related fields like energy efficiency & battery life, wireless & network bandwidth, miniaturization, and reducing the effective price per unit of computational power.
Important stuff! But it means a pretty solid machine from 10 or 15 years ago can still be plenty useful today.
Some emphasis on “pretty solid”. I still can’t really wrap my head around how well some sites (including probably this one) can bring an otherwise powerful enough machine to its knees. I’m pretty certain one could build a very representative “daily use” benchmark off of “highly useful” sites like Facebook or YouTube (and then I’m not even talking about the actual video playback itself which would have been the bottleneck not so long ago).
but can it run KDE-Linux…?