Found a solution that closes my question:

@Stable
val Arrangement.LastItemBottomArrangement: Arrangement.Vertical
    get() = object : Arrangement.Vertical {
        override fun Density.arrange(
            totalSize: Int,
            sizes: IntArray,
            outPositions: IntArray,
        ) {
            var currentOffset = 0
            sizes.forEachIndexed { index, size ->
                if (index == sizes.lastIndex) {
                    outPositions[index] = totalSize - size
                } else {
                    outPositions[index] = currentOffset
                    currentOffset += size
                }
            }
        }
    }

LazyColumn(
    modifier = modifier
        .fillMaxSize(),
    verticalArrangement = Arrangement.LastItemBottomArrangement,
)

https://stackoverflow.com/a/69196765/21932401