I've looked at both Smugglers' Lair on La Grenade, and Buccaneers' Camp on Hispaniola. Though I didn't find any black areas on the horizon at either place, there was a problem at Buccaneers' Camp. On the left is how it looked in 2021, on the right is how it looks with the 1st January installer:Please take a look at the hill in front of the smugglers camp. You can see some black areas over the horizon.
The problem is "RESOURCE\Textures\bump_city.tga.tx". I don't know why a jungle location is using a file called "bump_city", but that made me check the camp itself, which indeed shows the same problem:
So I put back the original version of "bump_city.tga.tx", which restored both the exit and the camp to their former glory:
@ANSEL: could you upload a screenshot, or for preference a savegame, showing the black areas on the horizon? It may be that they only appear at certain times of day, or I'm looking the wrong way. The problem is likely to be another of the new texture files and I'll need to track down which one it is.