RAR archive of 13.7 MB for HP motherboard DAG3PRMB8D0, with no further details in the name. The DA...MB...0 pattern is Quanta numbering, so Quanta is the ODM that produced the board for HP. The archive contents are not described, though the size suggests firmware or photos rather than a single schematic; extract it to check. If it holds a BIOS image, back up the original SPI chip before programming and verify the board number and flash capacity match.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @boardsscanrepo. Enginerys does not host this file.
How to open a .rar file
Compressed archive — the usual wrapper for a schematic + boardview pair or a BIOS + EC set.
7-ZipWinRARThe Unarchiver (macOS)