Here’s a tutorial on scratch building a 15mm mortar.
18th Century Warfare DBA Variant
Here’s yet another set of free wargames rules based on DBA. These are for 18th Century European and Colonial Warfare in 6mm.
The Void Lovecraftian Science Fiction RPG
The Void is a free RPG with a science fiction/ Lovecraft setting.
Rif War Resources
Steven’s Balagan website offers a rich page of information on gaming the Rif War of 1893 – 1927.
Saga Forge Solo Viking Campaign
Saga Forge offers a procedurally driven, zero prep solo campaign system for dark ages battles. It’s in beta testing, but may well be worth a try.