The HDR Batch Plugin lets you merge multiple stacks of bracketed exposures in Lightroom, and process them with an HDR preset you select from a wide range of styles.
The HDR Batch Plugin works in Lightroom 6 and Lightroom Classic CC.
Once you've installed the HDR Batch plugin, follow these steps to access and use it:
Note: If your bracketed sets all have the same number of exposures, it isn't necessary to group the brackets into Stacks. Instead just select all of the photos (then on the plugin's window, you'll choose the 2nd option in the Input section).
(Alternatively, choose File > Plug-in Extras > Photomatix Batch > Batch with Photomatix HDR)
See more details in the Using the Photomatix HDR Batch Plugin for Lightroom tutorial.