Footnotes are not included in main text selection. They are annotations kept separate from the main flow (essentially for layout reasons), though they are copied in a hidden way with text.
If you didn’t add any direct formatting when writing your document, footnotes are by default styled Footnote. All you need to do is customise this paragraph style.
You didn’t describe how you “cleared formatting”. By default, again, main text is styled Body Text but Footnote does not inherit from Body Text. Footnote* inherits directly from Default Paragraph Style. To nullify all specific settings in Footnote, press Reset to Parent in every tab then OK. Footnotes will then look identical to Default Paragraph Style.
The same can be done on Body Text to make it a duplicate of Default Paragraph Style.
PS: when asking here, always mention OS name, LO version and save format, even if you did so in some other question.