Yes, you can connect the LG Monitor 38WR85QC-W to your iMac 27-inch from 2019, provided you have the right cables and connections. Here are the important points:

1. connections: Your 2019 iMac 27-inch has Thunderbolt 3 ports in USB-C form, which is sufficient for connecting to the LG monitor.
2. connection: You need to connect the monitor to your iMac with a suitable cable. Since the LG monitor probably has USB-C or DisplayPort, you can use an appropriate cable.
3. system requirements: Make sure your Mac is running macOS Mojave 10.14.6 or a newer version to ensure a smooth connection.

However, it is important to note that the LG Monitor 38WR85QC-W has a resolution of 3840 x 1600 pixels, which differs from the native 5K resolution of your iMac. However, the connection should work without any problems as long as the connections and the operating system are compatible.