The issue with low TFR seems to be difficulty of forming relationships, not failure to have children once relationships are formed.

I'm imagining it becoming a social norm for single women to have (at least) a single child. Perhaps they'd team up to make raising them easier, forming loose family-like units. Romantic attachments would be optional.

One consequence of such a situation would be an incentive toward private positive eugenics. Women would prefer semen from top quality donors.