Why do SO many programs need to be closed during installation?

Like any browser, Any Office program, Discord, Slack, Skype, and several others.

Not a snark or anything, just FYI: This is not an issue in most (all?) GNU/Linux package managers.

Well, it also doesn’t happen, with all other MSI packages, I only remember ONE other.

@KurtRoesener: so what? Do those other packages all install fonts? shell extensions? register for MS document formats? …

Well, as indicated in that listed Bug Report only Fonts and Shell extensions are mentioned Not Registering for MS doc formats, So, in that case, Yes, I have installed MSIs that change those two items and not required killing any processes. Not that your comment was that constructive, to begin with.

Not that your comment was that constructive, to begin with

Huh? I point out the elements to note - and you tell that? fascinating. It’s better not trying to share anything with people to avoid that kind of attitude. Possibly people treat just any kind of communications as insulting, other that paid-support-like, such as “Dear sir/mam, in order to resolve your issue, could you kindly provide us the following information …”.

And my comment was meant to provide you with something to think about. having those items, one could start asking oneself, if those other programs didn’t require shutting down other processes on first install or on upgrades; if the items they installed (like those shell extensions) were likely to be actually used at the moment of upgrade (a shell extension is loaded when used first time in a session); did the upgrades require restarting afterwards, etc.

And all that added to the issue I cited in my answer, which tells about an option to reduce the likelihood of need to shutdown the processes - which those other MSIs coulde possibly have. So - who had made a not so constructive comment? Isn’t that the one who had been given an answer, but started to tell about something that cannot help anyone, like mentioning some (unnamed) other packages in unknown environment?

LibreOffice uses Microsoft’s MSI technology to install itself. In the installer, we don’t tell which programs to close, and even how to search for those programs. We only tell what to uninstall (our old versions) - which implies what files/registry keys to remove; and also what to install (again: what files/registry keys to put where).

Windows uses this information to search for programs that might use the resources being changed. Those programs might be Explorer that has LibreOffice shell extension loaded (the component that allows for getting the document information right in Explorer); or some programs using fonts or other shared resources. If a program uses something we install cannot be controlled by LibreOffice.

However, there’s possibly a way to decrease the number of required closes; and it’s tdf#117492. The proposal there might change from complete uninstallation of previous version followed by complete installation of updated version (which, naturally, touches every piece of LibreOffice) to only replacing/removing changed pieces. However, this needs thorough testing, which requires volunteers - and I’m waiting for a sign of interest in the comments on the issue page.