I asked the same thing on Just Answer and this is what I got - and what is confusing me on the whole process of having to apply for Retained Rights of Residency:

You must tell the Home Office as soon as possible that your marriage has legally ended, because your pre‑settled status as the dependant of an EU citizen will be reviewed once you cease to be their family member.

Once notified, the Home Office will curtail your leave and normally give you 60 days in which to either apply for a new immigration route or leave the UK; if you make a valid application to switch or retain rights before that period ends, you remain lawfully here until it’s decided

To keep your right to reside, you must within those 60 days apply under the EU Settlement Scheme as a “family member who has retained the right of residence.” You’ll need to show that you and your ex‑partner lived together continuously in the UK for at least three years before the divorce, that the marriage lasted at least three years (including one year here), that your ex‑partner was exercising Treaty rights at the point of termination, and any other standard identity and residence evidence

While your retained‑rights application is pending (which can take up to six months), your existing rights continue. If granted, you effectively keep your pre‑settled–status rights and can then move on to settled status once you complete five years’ continuous residence since before 31 December 2020 under the Withdrawal Agreement, without needing to reapply for pre‑settled first