Emacs Encoding – How to Switch Back Text Encoding to UTF-8

This seems like it was a problem of codepage (and hence specific to Windows) because Emacs internally used old Windows APIs that could only return chars that belong to your codepage (hence Windows turned ğ into a plain g before passing it to Emacs).

AFAIK this is not the case any more in newer Emacsen (we now use the newer APIs which use some kind of Unicode, probably UTF-16).

To show the encoding options dialog, go to Save As... and check Edit filter settings.

In order to avoid the slowness of Save As..., you could use a macro like this:

Sub SaveAsUtf8
    dim aUrl()
    dim fileProps(1) as new com.sun.star.beans.PropertyValue
    fileProps(0).Name = "FilterName"
    fileProps(0).Name = "Text (encoded)"
    fileProps(1).Name = "FilterOptions"
    fileProps(1).Value ="UTF8,CRLF,Liberation Mono,en-US,"
    oDlg = createUnoService("com.sun.star.ui.dialogs.FilePicker")
    oDlg.setMultiSelectionMode(false)
    oDlg.initialize(array(1))
    oDlg.execute
    aUrl = oDlg.getFiles()
    If UBound(aUrl) > -1 Then
        thisComponent.storeAsURL(aURL(0), fileProps())
    End If
End Sub

Set it to a hotkey or toolbar button by going to Tools -> Customize.

It could be modified to use a global variable and save to the previously used location.

UTF-8 WITHOUT the BOM, which I believe is called ASCII/US

No, this produces ASCII-encoded text, which will destroy most Unicode characters.

I do not see any filter options that can save without a BOM from LibreOffice. Instead, there are various command line tools such as iconv that can remove the BOM.

If you have some time, the best solution may be to create a Python or Java macro to read the Writer document and write to a file without the BOM. It could be done in perhaps 30 lines of Python code, or twice that much Java code. Note: I would not recommend doing this in Basic because of its poor file handling functions.