This model has been trained on base SD 1.5. It should be compatible with almost any checkpoint although quality may vary. It works with male or female characters. You can invoke it with the keyword "ww1ger". The LoRA weight depends heavily on what you want to do so it's hard to recommend something specific, I would say from 0.5 to 1 give the best results in normal scenarios.
This LoRA amalgamates multiple types of German uniforms during WWI, so it's not strictly accurate. For the helmet, I decided to only use the Stahlhelmet for now, but it's possible I will add some way to use the Pickelhaube later.
Images of costumes, cosplays, reenactments and original photographs from the war were used, but they all had some variation of the Stahlhelm. A total of 16 images were used.
I plan to make other LoRA themed about World War 1 so don't hesitate to give advice and feedback!