EPPlus VS ImportExcel

Like others, I recommend using the ImportExcel module. It uses and wraps EPPlus Software (EPPlus - Create advanced Excel spreadsheets using .NET (GitHub Project Old / New)) which is a DLL that is included with the ImportExcel PowerShell Module.

Their documentation looks okay. I doubt you're going to get many people familiar with a specific library here.

If you're copypasting stuff from excel, another approach I used in a different project is this package: https://github.com/EPPlusSoftware/EPPlus - which works in Blazor. You'd just let users drag/drop or upload their excel and import it, instead of copypasting

There is one Excel Library that I would recommend using in C# and that EPPlus. Its great and its free for non-commercial use. The API is simple to use and its got great documentation.

There is a Getting Started section in GitHub and complete API documentation on the home page

I've personally had a great experience working with EPPlus. It has both commercial and non-commercial/free licenses: https://epplussoftware.com/

Examples here that are similar to what you are trying to accomplish - https://github.com/dfinke/ImportExcel

Did you visit the GitHub repo and read the docs & examples? https://github.com/dfinke/ImportExcel

If you can create a reproducible example with sample data and code that re-creates the issue from nothing, post it to the project's issues on Github. The module's authors have been very quick to resolve the issues I've had, usually fixing the problem in a week or two.

If you're using scripting, I have to recommend ImportExcel for Powershell.

You might be able to use https://github.com/dfinke/ImportExcel to alter single cells in a csv file but I'm not 100% sure.

Have you looked at the examples? Examples

Maybe look at ImportExcel, it allows to put any list of objects right into Excel sheets, with insane customization capabilities.