I got my parents in their 70s to use Ubuntu for a few years now. All they use is a web browser and word processing application for .docx files. They used MS Word for years and I found Only Office has a similar UI and opens word docs.
At one point I gave them an older laptop running windows again and they hated it. They wanted Linux back.
From my experience, OnlyOffice provides better compatability with MS Office-files (that is, more so than LibreOffice). However, having used Powerpoint quite a lot in my professional life, and using OnlyOffice Presentation to make a slide deck now, that is an area where I unfortunately find it severely lacking. There's also the issue about their license - I am not all that familiar with it, but apparently they are not as free and open as they claim to be.
What ever happened to Open Office? That used to be the defacto replacement to Microsoft Office. I haven't used office tools on a personal computer in over a decade though, so I'm very out of the loop there.