DESQview/X sucked the wind out of DESQview's sails. It was, on paper, a massive upgrade. I had been running DESQview for years, with a dial-up BBS in the background.
But you couldn't actually buy /X. After trying to buy a copy, my publisher even contacted DESQ's marketing people to get a copy for me, and they wouldn't turn one over. Supposedly there were some copies actually sold, but too few, too late, and then /X was dropped. There was at least one more release of plain DESQview after that, but by then Windows was eating its lunch.
I'm booting and running Haiku on my Thinkpad. It's a from-scratch workalike of BeOS, and able to run Be software. Though, frankly, Be software is totally 1990s, so a lot of Linux software written for Qt has been ported to Haiku.
In the end I wound up with basically the same application software as on my Debian desktop, except running on Haiku instead of Linux. Haiku is noticeably snappier and more responsive than Linux+X+Qt+KDE, though.
Wine predates ReactOS. It was basically a FOSS duplicate of Sun's WABI.
I wrote a bunch of software in Borland Delphi, which ran in Windows, Wine, and ReactOS with no problems. Well, except for ReactOS' lack of printing support.
As long as you stay within the ECMA or published Windows APIs, everything runs fine in Wine and ReactOS. But Microsoft products are full of undocumented functions, as well as checks to see if they're running on real Windows. That goes back to the Windows 3.1 days, when 3.1 developers regularly used OS/2 instead of DOS, and Microsoft started adding patches to fail under OS/2 and DR-DOS. So all that has to be accounted for by Wine and ReactOS. A lot of third-party software uses undocumented functions as well, especially stuff written back during the days when computer magazines were a thing, and regularly published that kind of information. A lot of programmers found the lure of undocumented calls to be irresistible, and they wound up in all kinds of commercial applications where they really shouldn't have been.
In my experience anything that will load under Wine will run with no problems. ReactOS has some stability problems, but then the developers specifically call it "alpha" software. Despite that, I've put customers on ReactOS systems after verifying all their software ran on it. It gets them off the Microsoft upgrade treadmill. Sometimes there are compatibility problems and I fall back to Wine on Linux. Occasionally nothing will do but real Windows.
As a Linux user, I hated Flash with a passion. It mostly didn't work despite several Linux implementations. About the time they sorted all the bugs out, it went away. Good riddance.
I tried several "information management" and "knowlege management" programs over the years, but none of them worked the way I wanted.
My original method was a directory full of plain text files arranged by subject, that I brought up with my text editor.
Over the years I wrote a specification for a system tailored for my needs, that could manage different forms of media, notes, saved web pages, ebooks, and so forth. The spec grew until I set the project aside as more trouble than it was worth. In retrospect I wish I had kept going.
At the moment I'm using plain old hand-written subset of HTML linked to subdirectories arranged by subject. As time permits I will finish the (simplistic) custom browser, which will also let me annotate pages and edit files.
I have looked into some of the indexing programs that look inside files and index their contents in a searchable fashion. They all take a vast amount of storage space, probably because over the decades I have amassed a vast amount of data. After experimentation I decided to pass on the indexers as well. I have always managed things in a rigid hierachical arrangement, and it's pretty easy to find what I'm looking for. On the other hand, I know what's there and where I put it, which makes it easy for me. It would be much less useful for someone else.
Never underestimate the usefulness of a plain text file. It can be written, read, searched, and indexed by almost anything, should you wish to do so. Some of mine date back to the mid-1980s and MS-DOS 2.1, to OS/2 and Windows (briefly), Linux, and even Haiku. Every platform has subdirectories and some kind of editor; that's real portability. And if you ever have to deal with ancient machines that don't speak ASCII, much less UTF, there's probably some kind of conversion utility to let you move your files to IBM EBCDIC or DEC Sixbit.
If you're running emacs, the "org mode" add-in uses lightly-formatted text files organize data, which is then available within the editor. It's worth looking at if you're an emacs user, assuming you're not using org mode already.
The only true "system programming" I've done was in Microsoft Macro Assembler, a product I grew to hate with a passion.
A non-answer, but tangentially relevant:
I once fiddled with Forth, but never actually accomplished anything with it.
Several OSs are written in Lisp; in some of them the difference between OS and application is a bit vague. At the time none of them were available to me to play with.
I discovered Oberon and fell in love. My first real programming language was Pascal, and Oberon is part of the same family. Oberon consisted of a compiler, operating system, user interface, application software, and tools, all self-hosted on Oberon. There was even an Oberon CPU at one time. But Oberon turned out to be just an academic curiosity, and wasn't available for any hardware I had access to anyway.
I barely ever used it, but I noticed that MASM 5.1 is included (together with MSC 5.1 and various other Microsoft tools from 1988) in Microsoft's MIT-licensed MS-DOS repo. Trying some hello world level examples there was nothing obviously annoying about it so far.
The macros! Wtf were they doing with the macros! They didn't want to have a normal assembler that kept people writing maintainable assembly code. They just had macro stacked on macros (my memory here is literally 30 years old, I had to write windows 3.1 vxd drivers) and it didn't help, because they had to use the same registers you were using to do their work. An obtrusive non-abstraction that made life painful.
That happened to me six years ago. After a few weeks I quit beating my head against the wall, created an email account elsewhere, and eventually got most correspondents to use the new address. And I quit using Google services for anything else, too.
Every year or so I'll check to see if I can log in, but it just loops around variations of "two-factor authentication", which I had never used, and therefore have no answer to.
Cloudflare challenges seem to be becoming more and more frequent on my general internet use. Yep, "Cloudflare loop" is a thing. No, I'm not going to download and install a different web browser, dump all my cookies, or whatever other nonsensical "solution" they recommend.
I've become to hate Cloudflare with a seething passion.
But you couldn't actually buy /X. After trying to buy a copy, my publisher even contacted DESQ's marketing people to get a copy for me, and they wouldn't turn one over. Supposedly there were some copies actually sold, but too few, too late, and then /X was dropped. There was at least one more release of plain DESQview after that, but by then Windows was eating its lunch.