Technology and Re-Flavoring
Technology advanced both before and during The War to a point where radio communication, gas powered vehicles, electric devices, weapons, and many home conveniences and industrial advancements available during the 1920s of the real world are available throughout the world.
Generally, technology will be considered simply a part of the world and narrative, as not every piece of technology warrants a piece of gear or rules, such as telephones simply being a device that can be used to communicate across long distances and commonplace enough it can be assumed most business and many homes have one and they are fairly simple to use without a roll of any kind.
That said, any gear or abilities may be re-flavored as technology appropriate to the period and tech level. For example, Chainmail armor might be re-flavored as sturdy leathers or a flak jacket, or a healing potion might be re-flavored as a pick me up tonic. If the existing item has anything that could be considered a magical property, such as a Spellcast Trait, calling for a Spellcast Roll, dealing or preventing Magic Damage, or similar ideas, check with your GM and observe the Technology and Magic section.
If you think a piece of Technology might need additional rules to better represent its function, such as vehicles or bombs, work with them to develop rules that seem fair, balanced, and most importantly, fun!