Comment 8 for bug 1715185

anything regarding /opt/ definitely comes from unofficial packages. Also, just installing packages must not touch anything in a user's home.

About the "install hooks" you are referring about, just know that comparatively, very few packages have them, and nowadays they are mostly frowned upon as bugs in those can easily cause severe issues, and sometimes weird situations, so there is a tendency to move to other solutions. Telegam-desktop is a very simple application once built, so it doesn't have any reason to have "hooks" (which are called "maintainer scripts", btw).

So from what I gather, yours is a local configuration issue: the .desktop file in your home conflicted with the system one in /usr/share/applications/, and your desktop environment prefers the one in the home (correctly so), but since it refers to something non-existing it doesn't display what would be a broken icon. In a situation like this, indeed renaming the .desktop file in /usr would fix the situation as then the two wouldn't conflict anymore.

In such case, there really is nothing a package in the archive can do, as by policy it can't touch stuff in the user's home upon installation.