Spoofing the OS version to trick a buggy installer
Assuming that it's not baked into the installer, you can edit the version requirements for the app bundle.

Right click the app, hit Show Package Contents and open Info.plist. Look for a LSMinimumSystemVersion key, then change the value to your version of macOS.



You can also use Xcode's visual editor



It's possible you may need to do some more work though.


  NSBundle and CFBundle aggressively cache the contents of
  application bundles to improve performance. Although you edited the
  Info.plist, the Finder and Launch Services don't yet know that the
  application is any different.
  
  Running the following command in Terminal to touch the application
  bundle will force the Finder (and Launch Services) to re-register the
  application, thereby noticing the changes you made to the
  Info.plist:

touch "/Applications/My Cool App.app"

  
  After running that, deselect the application, then reselect it in the
  Finder, and then try launching it.
  
  Note that this won't necessarily guarantee that you'll be able to
  launch the app.


In the case that it's baked into the app more deeply, you can edit your macOS version at a system level. Note you'll also need to disable SIP if you haven't already.


  
  Boot in single user mode (hold down s during boot)
  Make file system readable:
  
  /sbin/mount -wu /
  Go the /System/Library/CoreServices directory:
  
  cd /System/Library/CoreServices
  Edit SystemVersion.plist
  
  nano SystemVersion.plist
  Change the version strings (note that there may be two of these in the .plist), e.g.
  
  
  

&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"&gt;
&lt;plist version="1.0"&gt;
&lt;dict&gt;
        &lt;key&gt;ProductBuildVersion&lt;/key&gt;
        &lt;string&gt;14E46&lt;/string&gt;
        &lt;key&gt;ProductCopyright&lt;/key&gt;
        &lt;string&gt;1983-2015 Apple Inc.&lt;/string&gt;
        &lt;key&gt;ProductName&lt;/key&gt;
        &lt;string&gt;Mac OS X&lt;/string&gt;
        &lt;key&gt;ProductUserVisibleVersion&lt;/key&gt;
        &lt;string&gt;10.10.4&lt;/string&gt;                // &lt;&lt;&lt;
        &lt;key&gt;ProductVersion&lt;/key&gt;
        &lt;string&gt;10.10.4&lt;/string&gt;                // &lt;&lt;&lt;
&lt;/dict&gt;
&lt;/plist&gt;

  
  
  Save and exit (Control-OControl-X)
  Reboot:
  
  reboot