There are two hyperlinks, one is only hyperlink without text,the other is the hyperlink with text in cell called anchor text, both of them can take you automatically to the target place.
if you want to remove all including hyperlink and cell text, you can use:
sheet.Range["B5"].ClearAll();
for the second case, you can remove hyperlink effect and keep the cell text content,see below code:
sheet.HyperLinks.RemoveAt(0);
You can see details:
Remove Excel Hyperlink[
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