Copy and paste any of the scripts into your console to apply the theme, no nitro, no modded clients needed!
Collection of all 21 Nitro Themes
in the file explorer type %appdata%
got to discord folder
go to settings.json
"DANGEROUS_ENABLE_DEVTOOLS_ONLY_ENABLE_IF_YOU_KNOW_WHAT_YOURE_DOING": true,
paste the above line
restart discord
also as a disclaimer these themes do not stick and get reset every time you refresh