In case you're wondering if the Apple 87W USB-C Power Adapter can be used to charge your LG G5 phone, we see how well this charger works with the phone when directly connected with a USB Type-C to Type-C cable.
We can see from the initial USB Power Delivery negotiations that the Apple 87W USB-C Power Adapter is constantly showing that it supports 12 watts (5 volts @ 2.4 amps) power profile.
The LG G5 takes some time to eventually request 12 watts (5 volts @ 2.4 amps) from the Apple 87W USB-C Power Adapter which it then accepts.
We also observe that the Apple 87W USB-C Power Adapter offers not only 12 watts (5 volts @ 2.4 amps) it initially declared but also 27 watts (9 volts @ 3 amps) and 86 watts (20 volts @ 4.3 amps) power profiles.
The LG G5 can be seen to take advantage of the additional power profiles to request 18 watts (9 volts @ 2 amps) and is accepted by the Apple 87W USB-C Power Adapter.
While the Apple 87W USB-C Power Adapter charges the LG G5 on a fully drained battery, we can confirm that it takes over 30 seconds for the phone to finally charge properly at around 9.9 watts (9 volts @ 1.1 amps) with the charger.