How to check a list is ordered using Fluent Assertions

It is possible to pass the options like:

listFromApi.Should().BeEquivalentTo(sortedList, opt => opt.WithStrictOrdering());

Yes. You can use BeInAscendingOrder with a lambda.

listFromApi.Should().BeInAscendingOrder(x => x.Property);

For extra clarity at the expense of performance, you can also assert on content equivalence:

listFromApi.Should().BeEquivalentTo(listOfObjects)
    .And.BeInAscendingOrder(x => x.Property);