I asked my AI friend to suggest me some open source games, and this is what I came up with :

Here are some open-source turn-based strategy games that emphasize mouse-centric controls (like point-and-click unit movement, army management, and tactical decisions, similar to Warlords 3). I've focused on those with gameplay vibes reminiscent of Warlords—hex/grid-based conquest, hero/army leading, and empire-building. All are free and licensed under GPL or similar.

LordsAWar!: A direct spiritual successor to Warlords II, where you command armies on a hex map, recruit heroes, and conquer territories via turn-based battles. Fully mouse-driven interface.

The Battle for Wesnoth: Fantasy-themed hex-based strategy with recruiting leaders, advancing units, and multi-campaign stories. Highly polished, entirely mouse-controllable for movement and combat.

Advanced Strategic Command: Inspired by Battle Isle, it features grid-based tactical warfare, resource management, and AI/multiplayer modes—all navigated via mouse clicks for unit orders and terrain interaction.

LGeneral: A clone of Panzer General with WWII-themed campaigns; move divisions across maps, plan attacks, and upgrade forces using simple mouse controls.

MegaMek: A BattleTech simulator for hex-based mech and vehicle combat; assemble forces, roll dice for attacks, and execute turns purely with mouse inputs.

Tanks of Freedom: Modern take on capturing bases with tank squads in short campaigns; quick, mouse-only unit deployment and pathfinding on grid maps.

FreeOrion: Galactic 4X empire-builder like Master of Orion, involving exploration and fleet commands via intuitive mouse-driven menus and ship movements.

I'm simply sharing with you all what l came across, and looking forward to hearing if you've played any of these, or something similar.