MekHQ helps users manage and maintain their forces between tabletop games on tabletop, other virtual tabletops, or in MegaMek. It does so by recreating the BattleTech rules for managing a unit, handling personnel, salvage, and repair. The program features financial bookkeeping, pilot skill progression, ranks, recruitment and parts management, as well as strategic campaign planning. It includes a full, year-accurate, database of planets utilizing the Sarna Unified Cartography Kit with unofficial expansions as per here.
Though it supports all kinds of units, from support vehicles to infantry and WarShips, as of 2021, the automated AtB program is geared towards mercenary units, and has limited support for pirate or faction-style organizations.
A solo play mode, called "Against the Bot" is provided and generates missions, scenarios with detailed, appropriate opposition, and victory tracking. 
Like its associated program, MegaMek, MekHQ is Java-based, and runs on any system that supports their current Java version.