You can remove watermark by downloading dgvoodoo.conf for your version of dgvoodoo (lutris default should be 2.8.2) and setting dgVoodooWatermark to false.
NOTE: dgVoodoo is sensitive to config versions and refuses to load config if versions don't match!
Lutris dgVoodoo can be configured the same way as any other configuration by placing dgVoodoo.conf into the game folder.
NOTE: dgVoodoo is sensitive to config versions and refuses to load config if versions don't match!
You can download some of the dgvoodoo.conf files for specific versions from this repo as some of them are not (easily) optainable anymore.
PS: If you can't find your version try changing Version parameter in dgVoodoo.conf to your version of dgVoodoo. For example for version 2.8.2 you write Version = 0x280 and for 2.83.3 you write Version = 0x283