Today I did my first advanced spreadsheet on LibreOffice after switching to Linux, and it handled itself pretty well. I had to search for some features on the web at first, but after I got it down, I felt comfortable using it. Also, LibreOffice’s default menu layout is not pretty, but I can find all of the functions with just a click, unlike MS Office’s ribbon menu where I had to click around to find what I was looking for. Sorry for bad English.
Yes, in theory, although tricky to set up. What it cannot do, at least not without fiddly modules, and even then nowhere near as well as the cloud competition, is any kind of collaborative document editing. Which is where the world is at today.
You said “in the real world nobody much is doing the latter”.