What is the tag question for sentences like;

Everyone likes incecream.

Everywhere was dark.

and so on.

Thank you
Everyone likes ice cream, don't they?

Everywhere was dark, wasn't it?

and so on.-- I don't know what this refers to.
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Thanks Mister Micawber.

Since we treat everyone as singular, I thought we have to use singular subject for it in tag questions.

Thanks for clarifying.
Everyone likes ice cream, don't they? -- That's the only reasonable tag. One more reason to accept 'they/them' as singular pronouns of indeterminate gender.
Everyone likes ice cream. Question Tags
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