Unlock My Excel File

I have a single-sheet Excel workbook (.xlsx) that I originally built in Excel in about 2018. It contains nothing but text, yet years ago I set an open-file password that I can no longer recall. Because I have no backups, the file is now completely inaccessible.

I need a reliable way to regain access—either by removing or recovering the password or, if that proves impossible, by extracting the plain-text contents so I can rebuild the sheet from scratch.

Deliverables
• A copy of the file that opens normally in modern Excel (2016 or later)
• Alternatively, a text or CSV file containing every character stored in the locked sheet

Please outline your proposed method and any tools you will use to ensure the integrity of the recovered data.