I now had a deeper look into the source code of main/tdelibs/tdeio/tdefile/kpropertiesdialog.cpp and maybe found the root cause.

In line 2088 
      bool allDisable = true;
is defined to enable/disable the OK button. This value is only set to false in line 2100
  ...
  // Draw Checkboxes
  bool allDisable = true;
  TQCheckBox *cba[3][4];
  for (int row = 0; row < 3 ; ++row) {
    for (int col = 0; col < 4; ++col) {
      TQCheckBox *cb = new TQCheckBox( gb );
      if ( col != 3 ) theNotSpecials.append( cb );
      cba[row][col] = cb;
      cb->setChecked(aPermissions & fperm[row][col]);
      if ( aPartialPermissions & fperm[row][col] )
      {
        cb->setTristate();
        if( d->canChangePermissions ) {
+++       allDisable = false;
        }
        cb->setNoChange();
   ...
As far as I understand, the button is only enabled if more than one file is selected and the file permissions of the files differ in some flags. 
But this dialog the only interface to the flags "Set UID", "Set GUI" and "Sticky". So you can not change this flags for a single file. Maybe enabling the OK button, when you are allowed to change permissions (canChangePermissions) and not only if aPartialPermissions is true, solves the problem.

Thanks Stef


On Thursday, 11. July 2019, Sl�vek Banko wrote:
> On Thursday 11 of July 2019 19:21:14 update wrote:
> > Hello,
> > since upgrading from tde 3.5.13  to 14 and ubuntu precise to xenial
> > (linux-4.4.0 and 4.15.0), the OK button in the "Advanced Permissions"
> > dialog of Konquereor is not enabled any more. The file system is ext4
> > with acl and user_xattr enabled.
> > Is this my local problem, or has any one else this issue too?
> >
> > Thanks
> > Stef
> 
> I am using the XFS file system, which has ACL in the basic features, and I 
> see the same problem with setting advanced permissions.
> 
> These bug reports seems to be related:
> 
> + bug 402: Advanced Permissions button in d3lphin is not accessible if not 
> owning the file 
> http://bugs.pearsoncomputing.net/show_bug.cgi?id=402
> 
> + bug 2375: [Regression] Cannot change advanced permissions with tdesu 
> konqueror 
> http://bugs.pearsoncomputing.net/show_bug.cgi?id=2375
> 
> Cheers