First, the minor bugs and questionable code; here is a diagram of your control tree:

# MainWindow  $MW
# Frame         Frame1
# Labelframe      SourceFrame
# Label             SourceTypeLabel
# Optionmenu        SourceTypeMenu
# Frame             sourceoneFrame # Mutually exclusive
# Frame             sourcetwoFrame # Mutually exclusive
# Label             StringLabel
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• Shouldn't $tkobjects{'StringLabel'} be a child of (alternately) sourceoneFrame/sourcetwoFrame?
• The text for $tkobjects{'StringLabel'} is always "string two"; it should be "string one" for the first case.
• $tkobjects{'StringLabel'} gets overlaid on each menu swap; should it get explicitly destroyed first?

To fix the abort, I reached the same conclusion that you did; wrap sub{ } around the value side of

  -command  =>
    $typeframes{'source'}->{ $config{'sourcetype'} }->( \%tkobjects ),
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Why did the original version fail? Because -command expects a coderef, but your code is an *immediate* call to
(Let's see: $config{'sourcetype'} is 'one', and $typeframes{'source'}->{'one'} is &makeSourceoneFrame, so ...)
makeSourceoneFrame(\%tkobjects), which returns a Label object. When Tk tries to call the Label as a coderef, boom!

By wrapping it all in sub{ }, you create a closure where (for example) $config{'sourcetype'} will supply its hash value as of the time of invocation, instead of at the time of definition. See perlfaq7 and perlref for more on closures.

When I refactored the code to reflect the closure, I came up with this version; it replaces the code just before MainLoop:

    # $option_command will be an anon sub,
    # with sole access to %typeframes.
    my $option_command;
    {
      my %typeframes = (
          'source' => {
              'one' => \&makeSourceoneFrame,
              'two' => \&makeSourcetwoFrame,
          }
      );
      $option_command = sub {
        my $option = shift;
        $typeframes{'source'}->{ $option }->( \%tkobjects );
      }
    }

    $tkobjects{'SourceTypeMenu'}
      = $tkobjects{SourceFrame}->Optionmenu(
#        -variable => \$config{'sourcetype'}, # No longer needed!
        -command  => $option_command,
        -options => \@TYPES
      )->grid(
        -row    => 1,
        -column => 1,
      );

    # By naming the anon sub (via variable), we avoid
    # repeating code here.
    $option_command->('one');
    # Actually, we don't have to manually invoke $option_command;
    # it got called with the first (default) option when
    # the OptionMenu was created!

    MainLoop;
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