OK found it. LibreOffice has a bug. When you choose "A4 borderless" and click "OK", it's not saving your choice for some reason. Used a converted version of my document as a PDF. 'Document Viewer' is working great with borderless.
(If you're reading it and still failing with your printer, maybe it's not supprting borderless. You should check it. Read about your model)
OK found it. LibreOffice has a bug. When you choose "A4 borderless" and click "OK", it's not saving your choice for some reason. Used a converted version of my document as a PDF. 'Document Viewer' is working great with borderless.
(If you're reading it and still failing with your printer, maybe it's not supprting borderless. You should check it. Read about your model)