How does this work in the real world? What’s the overlap between daily living and unconditional love?
I guess that means leaning forward into daily living, leaning forward with the intention to receive and to give, to absorb and to act, in whatever configuration and arrangement is appropriate for your identity, your value model, your brain and your body.
It seems the obvious trick to all of this is removing friction and resistance you carry in implementing this.
It seems the obvious lubricant is to sense what is behind each worthy concern that constitutes a friction, behind each inherited wisdom that is presumed to be a safety rung and not a carbuncle.
This process enables actions to become fit for purpose, and learning how to do this, all without the baggage that you bring to the table, the identity that it carries.

The trolley problem is just another aspect or layer of all of this, as is animal husbandry.
Unconditional love is independent of pulling the track lever or despatching an animal.
They are connected only if you want (the implied sanctity of) unconditional love to pressure and act on the other two.
You will want this if you are demanded to provide leverage and conditions against freely pulling the track lever or despatching an animal.
(Every other concept and mediation will also be called to account in the real world of rights, legality, accountability).
If you trust the unconditional lover, then such leverage and conditions and guarantees are not required.
But this is mostly beside the point in this brief segue.
The point is that the two worlds can be considered separately, and thereby free you up to consider each separately and independently of our usual value process anchored in our familiarity.

“Unconditional love is about caring for the happiness of another person without any concern for how it benefits you. “
Unconditional love is seeing the light and spirit in another person, and willing his surrounding to let it shine and flower, whether now or over lifespans. You are only present as another light and spirit (however that might interact with his), and a physical presence for practical solutioning, and generally a channel for other greater better minds and spirits to intervene.

“Some say that the only person you are capable of loving unconditionally is yourself. “
I have no idea how this would work by itself.

“Others say that the only unconditional love that exists is the love between a parent and a child. “
What survives of the original simple description (of unconditional love) in the relationship of parent to child entirely reflects their capacity for unconditional love elsewhere. Sure, parental love should scrub their relationship a bit cleaner of conditions. But they are no more able to spontaneously evolve a new level of loving. Which takes us back to asking how to elevate above both in order to accept each other unconditionally for who they are.
Segue: in the end, we are pastoral carers for our children. Our role is to have them be who they are, from the first moment. The more baggage and guidance we give them, the less they will be who they are. Part of our baggage is our inability to distinguish between baggage and wisdom.
In the end, the wisest question we can ask ourselves as we pastor them is: “what can I arrange so they learn how they learn, and that the who that is most present in that learning for the rest of their life is probably themself?”
In the end, the worst thing we can do is tell them. Anything.
In the end, the best thing we can do is ask them. Everything.

“But can this exist between two adults? It is said that by dropping one’s ego and letting go of one’s individual preferences and needs, one can love unconditionally. “
Yes, amongst other things that make up identity.

“But isn’t this a recipe for uniformity? “
You wouldn’t believe the variety and splendour of unpredictable, spontaneous, creative, courageous and original perception and expression we have, after we drop the conditionality and its constraint that makes up so much of our identity.