... is home usage such as games and entertainment. That is the purview of Windows and the area Linux is most interested in.
A: Windows is interested in many things. It doesn't actually make all that much money from games and entertainment. In terms of windows sales, I think the order is (1) servers, (2) professional desktop users, and (3) home users. Furthermore, today Microsoft is more of a cloud company, and somewhat of an application company (Office and related stuff), and only to a small extent an operating system company.
B: The statement "the area Linux is interested in" makes little sense. There are many Linuxes. There is the foundation, which is funded by a whole lot of entities, and employs Linus and a few other people, but does not have power over everything. Kernel development is done in many places, without central command and control. There are lots of distributions, the biggest ones being RedHat, SUSE, Debian, Ubuntu, and so on. Nobody knows what their market share is, and even more interestingly, comparing the market share among servers, desktops, and machines with paid support is meaningless. Each of those distributions has their own interest and goals.
One thing that is very clear is that the market share of Linux (and by extension all free Unixes) on the desktop/laptop market is tiny. That market is still dominated by Windows, with ChromeOS in second place, and MacOS in third, and all the rest are in the single-digit percent. So the question "what is Linux interest in the desktop market" is not only meaningless, it is also irrelevant.
Occasionally one will read about some FreeBSD developers running FreeBSD on a Mac.
I know a few BSD developers, and my hunch would be that among them the most popular machines are Macs (running MacOS) and Chromebooks. That's because real development doesn't happen on one's desktop machine, but on remote machines, so the choice of what to use as a user-interface and what to code on becomes decoupled.
I came to Linux 25 years ago because ... But since Intel, IBM and Microsoft rule its destiny, ...
The statement that Intel, IBM and Microsoft rule Linux' destiny is complete nonsense. Paranoid nonsense. It is true that Intel and IBM (as the new corporate home of RedHat have some influence, but many other companies and people also have influence. Microsoft has very little influence.
In the last decade, Linux has become the dominant "Unix" server variant in every IT department I have seen. It has a major presence, often rivaled in numbers only by Windows servers.
Exactly correct. Among the TOP500 supercomputers, Linux has 100% market share. Let me repeat that: There is no single supercomputer worth mentioning that runs an OS other than Linux. Among cloud machines (at the companies often referred to as FAANG, plus their Chinese counterparts), Linux servers absolutely dominate (with a little Windows here and there, and a small number of FreeBSD-derived machines at "N"). In IT departments, it is as you said: overwhelmingly Linux, a little Windows.
Solaris is effectively gone. AIX is being slowly and quietly deprecated.
While that is true, there is interestingly still a thriving market in older OSes. AIX is still sold and supported (it is the last major Unix still standing). You can still get HPUX on Itanium, but that will end in a few years. But non-Unix OSes are still shipping, and have commercial support contracts, including Nonstop (Tandem's old operating system), OpenVMS (the old Digital Equipment OS), MVS/TSO and VM (today in the guise of zOS on IBM mainframes), GCOS (formerly known as GECOS, the GE -> Honeywell -> Bull operating system, still enhanced and supported by Bull), IBM iSeries (formerly known as AS/400, which enhanced the series of System 34, 36 and 38 operating systems), and even HP's old MPE can still get support (I think only from third parties today). While all this is only in support of legacy applications, it is still a multi-billion $ industry. One could actually say that IBM made all the money for buying RedHat by selling mainframe computers, which use a 50-year old CPU architecture and run a 50-year old OS.