flux-setup.4.111.0.0.exe /D=%ProgramFiles(x86)%\Flux

You can refer to https://nsis.sourceforge.io/Docs/Chapter3.html for details.

Another minor issue observed is that after keeping flux running under %ProgramFiles(x86)% or %ProgramFiles%, clicking the "Update" button from the 4.118 update notification will do nothing. That may be caused by a lack of administrator priviledge. In that case, remember to rerun it as adminstrator or disable the update notification.

Often, installers ask whether to install for all users, or just for an individuel user of the computer. Maybe one could think of adapting the installer accordingly?

However, even if f.lux could be installed "globally" for all users, there would be two further options: (i) each user should have the possibility to adjust the app to his/her own needs and preferences, or (ii) the settings made by one user apply to each user at a time.

On a box with several "users" such as a normal user, an admin, a backup-user, a special user for banking and the like, which are in fact, however, the same real person, option (ii) would be really quite nice ...