can not compile 9.3

According to the configuration guide, this error can be caused by the following:

NOTE: References to VI.DialogEngine and other libraries that use System.Windows.Forms cannot be used in scripts anymore.

docs.oneidentity.com/.../scriptmessageoutput.html

I am aware of this, and agree.  However, DlgMth is not my code.  How am I supposed to fix this?  Where is this code being stored?  

Bigger question is how it's possible that a NuGet package that only exists in 9.3 can not be .NET 8 compatibel?  

The NuGet error "package VI.DialogEngine 9.3.0-311513 is not compatible with net8.0" can be misleading. The package VI.DialogEngine 9.3.0-311513 is net8.0-windows. net8.0-windows is ".Net 8.0 windows only". net8.0 flagged packages must not reference net8.0-windows packages as dependency. As this would make them net8.0-windows too.

Are you sure there are no custom DialogMethods or changes to the code of default DialogMethods? You can check with:

-- check for custom DialogMethod entries
select * from DialogMethod
	where dbo.QBM_FCVObjectKeyToModuleOwner(XObjectKey) = 'CCC'

-- check for custome changes to DialogMethod.MethodScript
select dm.*
	from DialogMethod dm
	join QBMBufferConfig bc on dm.XObjectKey = bc.ObjectKeyOfRow
	where bc.TableName = 'DialogMethod'
		and bc.ColumnName = 'MethodScript'

Oh.  Now I understand.  These are custom (Launch-Pad) Tasks that got added back in 2018.   I was going crazy trying to figure out where this code was coming from.  The Upgrade lets you lock incompatible scripts, but it ignores Tasks.   I wanted to remove these in Designer, but Designer is not usable.  Everything you click produces error after error about missing script-assemblies, followed by an empty screen.  I had to disable them in SQL...

update DialogMethod
set IsDeactivated = 1
where dbo.QBM_FCVObjectKeyToModuleOwner(XObjectKey) = 'CCC'

Unfortunately I still can't compile.  DB Compiler tells me "The database log contains messages that may prevent successful processing. Click [here] to show or hide these messages.".  If I click on "here", it says "Processing is disabled (wait for compiler)."  duh.  One step forward.  Two backwards.

Discovered that if you launch the Compiler from Designer or from the Launch Pad, it just sits there waiting for something to happen that will never happen.

Trick is to start the compiler from the OneIdentity directory and log into the DB.   Then it lets you compile the DB.   Now I have errors that I can deal with....

You might be running into this issue - support.oneidentity.com/.../delays-with-waiting-for-the-compilation-screen-to-become-available