Import text as text field

I do this all ofthe time CKO - however I recommend against Excel, or use it as a last resort. Excel's greatest strength in being able to do what you want with it is its greatest weakness for ingestion into Power BI. People will merge cells, type CTRL-ENTER returns in cells, and all kinds of things that will either mess the report up visually or break the refresh entirely. You can mitigate this with protecting fields, locking workbook settings, etc, but it is never foolproof.

I just implemented a report where users would key in comments for Purchase Orders with delivery comments - why is it late, what is the latest data from the vendor, etc. I used Lists in Teams for this, which is just a SharePoint list. You have total control over the data. A numeric field simply cannot accept data in SharePoint Lists. In Excel, if you paste info, you can bypass any kind of data validation restrictions. If you have Office 365 in your tenant, I strongly suggest a SharePoint List for this as they are easy to set up - and even easier through the Teams Lists app. Then you just connect to the List through Power Query by pointing to the SharePoint URL of the Team/SP site. 

Other options include Microsoft Forms, which puts a basic UI on an Excel file, but people can still get to the underlying Excel file. It is still better than a direct Excel file. You can get really fancy with a Power Apps interface and then you control even more than SharePoint Lists - but that is more work. In order of prefrence for me:

1. SharePoint List - super easy to use and set up.
2. Microsoft Forms - easy to set up, nice UI, but still has Excel underneath and can be an issue.
3. Power Apps on any datasource you want (Excel, SharePoint List, SQL Server, etc.)
4. Anythign else
5. Excel 😀

To make it work you just need a key field. In my example above. the user filled in 2 fields. The PO number - and this is what you merged with in Power Query to bring the data into the model, and a Comment field, which I think I set to 512 chars so they could write enough but not put an entire novel in there. The nice thing about a SharePoint list is it automatically tracks their user name, email address, add date/time, change date/time so you can add that metadata to the report too if desired. An Excel list would require the to fill all of that info out.