In Pages v14.2 on macOS Sequoia v15.1.1, I can select all page content from one Pages document with text flowing around an image, and simply paste it into a blank Pages document. The exact formatting is retained in the new Pages document. This is also the same behavior that I observe when using the same donor document with Pages v12.1 on macOS Big Sur 11.7.10, and Pages v11.1 on macOS 10.15.7. To select all content on the donor page, I click at the page beginning and drag downward to that page's end to select everything (including the image(s)).
An alternative is to export the donor document to PDF; open that PDF in Preview with thumbnails enabled, select the donor PDF page, and then drag and drop that thumbnail over onto the Pages recipient page. You have just placed a PDF object into Pages and you can position and resize it as you see fit. I just tested this in Pages v11.1 on macOS Catalina 10.15.7 and it is supported.