Is it possible to connect an Excel table or column from an Excel table with an attribute table in QGIS?
I think you need a very simple join operation. However QGIS can handle csv or text format. Alternatively you can install the spreadsheet Layer Plugin which allows to manage excel file directly. For join operation you can follow the official guide
If, you can upload your excel file directly to QGIS.
Simply load your excel file as a
vector layer, as if you were going to load a shapefile or geopackage.
If your excel file has several sheets it shows you the option to select the sheet(s) you want to incorporate into QGIS.
Recommendations: Before loading the excel file format your data as close as possible to a table of data.
After you have loaded the file, open the layer properties dialog box, go to the join option and link the common field of your attribute table to your excel sheet.