Dear User,
Thank you for reaching out Microsoft 365 community. To get the file "download" instead of "open", please modify the download URL like below.
https://<yourdomain>.sharepoint.com/sites/<yoursite>/_layouts/download.aspx?SourceUrl=<document-URL>
Eg.
For the <document-URL>, please locate the file on sharepoint > right click it > Details > scroll to bottom and copy path.
We are committed to ensuring you have a smooth experience with Microsoft 365 products, and we appreciate your patience and understanding as we work through this challenge.
If there is anything further we can assist you with in the meantime, please do not hesitate to reach out.
Best regards,
Sophia