Economic activity is not a requirement for naturalisation.
Re. application with settled status, the "Statement of Intent" says:
7.7. Holders of settled status (indefinite leave to remain) under the scheme will be able
to apply for British citizenship if they wish and otherwise meet the requirements for this:
• Immediately, if they are the spouse or civil partner of a British citizen (and they have
been lawfully resident here for at least three years), or if they were granted
• 12 months after the date on which they acquired the right of permanent residence
under the Free Movement Directive, as evidenced by a document certifying
permanent residence or a permanent residence card, issued by the UK under the
EEA Regulations; or
• Otherwise, 12 months after the date on which they were granted indefinite leave to
remain under the scheme.
Read the full document:
https://assets.publishing.service.gov.u ... e_2018.pdf
Note that the document is not a statement of law! By the time it is enacted wording and meaning might be different.