winuser_pl wrote:This computer is just to old for anything "modern". You will need to recompile the kernel with your own flags, disabling many many features and security flags. The next step would be to rebuild the window manager.
But even if you could manage to start the kernel and window manager you will get only software rendered graphics - this plus 486 architecture will result in a horrible slow OS.
But if this is not an issue for you, then you will face another problem - there are no software for 486 architecture. The current software is not a monolite like in the 90s, where you had a source package and you had to rebuild it. Today you will have to rebuild all of the dependencies as well which is just a pain in the ass because they must be build recursively to "the ground zero". The amount of the work is insane and it is impossible for any person who is not a senior dev.
What you describe here is exactly what Gentoo does for you. You specify the architecture and the flags, it handles the dependencies and compilation. It's harder than "click here to install", but so long as you have a basic understanding of the hardware you are using and how Linux generally works (libraries, frameworks etc), it's by no means impossible and you definitely don't need to be a dev, let alone a senior one.
I once shoehorned a Gentoo install including full graphical UI into a P266MMX laptop with 32MB RAM. It took me over two weeks of compile time (couldn't get distcc to work), but I was left with something usable - and far more usable than a less optimized install of an older Debian etc would have been, as cutting out unneeded support shrunk binary size significantly (~25%), which is very, very relevant when you have so little RAM. Now, that was a while ago, but the same principle should still apply.
OP tried that and it works in principle, he just has stability issues that he is trying to troubleshoot.
Forget about anything modern. You could try something like source code from 13-15 years ago and then rebuild it. Remember, we software developers are guys who like to keep things clean, many of the improvements are introduced by the cost of backward compatibility over the years. That's why it is not always just a thing of rebuilding the current source code, because the legacy part of code is thrown away at some stage of refactoring.
There's "modern" and "modern". Of course a 486 isn't going to do anything even remotely modern graphically speaking, but that's a sideshow in the Linux world, under the hood it's all CLI and that doesn't require a Ryzen + Vega combination. Also, you don't need something as bloated as systemd to boot a system... A 486 can run ssh, so can communicate with and control other, newer, far more powerful devices. By running an up-to-date version, it can connect to internet safely. You can do bash scripting, so there's nothing stopping you working in the Unix way, stringing multiple simple programs together to get complex stuff done. None of those simple programs inherently requires any more power than a 486 can deliver, and few of them will have crazy dependencies that don't make sense on old hardware.
So there's nothing inherently unrealistic about getting up-to-date Linux running (in CLI only, or with a very simple X+WM combo) on vintage hardware. However if it doesn't work under Gentoo your options are limited as pretty much no one precompiles for dinosaurs like this anymore. Which is why I recommend NetBSD. It definitely runs on a 486DX with 32MB RAM and definitely has up-to-date networking including ssh.