I have the experience with my 2 parents, who at an age between 80 and 90 years have used during several years computers with Linux, without any problems ever and without even knowing what is "Linux" and that they are using "Linux".

Obviously that was possible only because I have installed and configured all programs for them. Nevertheless, that is also true for Windows, because most Windows users would never be able to use Windows, had it not been already preinstalled on their computers by professionals.

I have installed professionally both Linux and Windows on many computers with slightly less usual hardware, as they were embedded computers, and surprisingly, I had more cases when Linux just worked, while making Windows Enterprise work required several days of efforts, and the unexpected solution for Windows was not in any nice graphical menu, but in the invocation of some obscure Windows command-line utility, using some magic command-line options, which had been found by searching the Internet for forums of Windows users that had encountered the same problems.

So from my experience, the ease of use of Windows vs. Linux is greatly exaggerated, some times any of them may just work after a default installation without any user intervention, but also any of them may require a professional for installation and configuration.

In the case of my parents, my mother had little experience with computers and I put her on Linux since the beginning. She used the computer mainly to watch TV shows, to watch movies, listen music or read books. Because I had installed and configured all the programs needed by her, it was very easy for her to do any of these activities. Moreover, she did these mostly by using an infrared remote controller, and the programs were configured to map all commands to the buttons of the remote controller. So it really did not matter whether that was Linux or Windows, as the main user interface learned by her were the buttons of the remote controller and their effects on the graphic display.

My father was relatively experienced with Windows, and he used it also at home for some time, until Windows was blocked by some ransomware. After wiping Windows, I did not restore it, but I switched him to Linux.

He was the kind of user described by you. Besides Internet browsing, he was writing and editing many Word documents and Excel spreadsheets, he was recording movies, writing subtitles for them and editing subtitles. He also organized a large collection of legal documents.

After I had installed and configured to suit his preferences all the programs needed for his activities, and after I have also written a few scripts to ensure that anything that he wants to do can be done with a click, without the need of selecting extra options, he succeeded to do everything easier than previously on Windows (where I had not attempted to help him by writing scripts to automatize his more frequent activities).

My father had only one problem during the transition from Windows to Linux, which was the transition from MS Excel to OpenOffice/LibreOffice Calc, as he had liked better Excel. Eventually he became habituated enough with Calc, so he no longer missed even Excel.

Actually, in my experience, the older versions of MS Office work even better on Linux than on Windows, for some unknown reason (via Crossover or Wine), so I could have let my father continue to use MS Office under Linux, but the last MS Office versions that I have bought have been those from 2003 and 2004 and I wanted to wean my father of them, as they had become too old and I did not want to buy any new version of MS Office, as I dislike the modern MS Office UI, which IMO is much worse than the traditional MS Office UI.