Stellaris 4.5.2 “Cygnus” is out on Steam, GOG and Microsoft Store. Its clearest balance change sets armor upkeep to the same energy and alloy cost as a shield of the same tier; armor previously cost double. The Steam post lists checksum 9776.

Armor costs less to maintain
At each matching tier, armor and shield upkeep now cost the same energy and alloys. The patch notes say armor previously cost twice as much.
At the start of a game, Fleet Doctrine, Weapon Preferences and Defense Preferences are now assigned randomly, with a weighting toward the empire’s defaults.
New options for nomadic empires
Nomadic Knights of the Toxic God who tame or kill the Toxic God can use their Arkships to detoxify Toxic Terraforming Candidates and turn them into habitable worlds. The update also adds “Weapon Preferences (Arkships)” and “Defense Preferences (Waystations)” for nomadic empires.
Defense platforms gain weapon and defense preference policies, while starbases lose the “strike craft” weapon preference policy.
Combat lockup fixed
The patch fixes a bug that could leave fleets stuck in combat indefinitely when one of their ships moved out of weapon range. The full change list appears in theofficial Stellaris post.
See alsothe Stellaris game page.