Unit filtering actually comes in 2 flavors - one for "unit templates", BaseUnit, and one for "actual units in the field", MapUnit. This should be reflected in the parameter names.

core/src/com/unciv/logic/civilization/CivInfoStats.kt

@@ -6,6 +6,7 @@ import com.unciv.models.metadata.BASE_GAME_DURATION_TURNS
 import com.unciv.models.ruleset.BeliefType
 import com.unciv.models.ruleset.Policy
 import com.unciv.models.ruleset.Unique
+import com.unciv.models.ruleset.UniqueType
 import com.unciv.models.ruleset.tile.ResourceType
 import com.unciv.models.stats.Stat
 import com.unciv.models.stats.StatMap
@@ -22,7 +23,7 @@ class CivInfoStats(val civInfo: CivilizationInfo) {
     private fun getUnitMaintenance(): Int {
         val baseUnitCost = 0.5f
         var freeUnits = 3
-        for (unique in civInfo.getMatchingUniques("[] units cost no maintenance")) {
+        for (unique in civInfo.getMatchingUniquesByEnum(UniqueType.FreeUnits)) {
             freeUnits += unique.params[0].toInt()
         }
 

core/src/com/unciv/logic/map/MapUnit.kt

@@ -943,6 +943,8 @@ class MapUnit {
             return filter.removePrefix("{").removeSuffix("}").split("} {")
                 .all { matchesFilter(it) }
         return when (filter) {
+            // todo: unit filters should be adjectives, fitting "[filterType] units"
+            // This means converting "wounded units" to "Wounded", "Barbarians" to "Barbarian"
             "Wounded", "wounded units" -> health < 100
             "Barbarians", "Barbarian" -> civInfo.isBarbarian()
             "City-State" -> civInfo.isCityState()

core/src/com/unciv/models/ruleset/Unique.kt

@@ -15,11 +15,29 @@ enum class UniqueParameterType(val parameterName:String) {
             else null
         }
     },
-    UnitFilter("unitType") {
+    MapUnitFilter("mapUnitFilter"){
+        val knownValues = setOf("Wounded", "Barbarians", "City-State", "Embarked", "Non-City")
         override fun getErrorType(parameterText: String, ruleset: Ruleset):
                 UniqueType.UniqueComplianceErrorSeverity? {
-            if(ruleset.unitTypes.containsKey(parameterText) || unitTypeStrings.contains(parameterText)) return null
+            if (parameterText in knownValues) return null
-            return UniqueType.UniqueComplianceErrorSeverity.RulesetSpecific
+            return BaseUnitFilter.getErrorType(parameterText, ruleset)
+        }
+    },
+    BaseUnitFilter("baseUnitFilter"){
+        // As you can see there is a difference between these and what's in unitTypeStrings (for translation) -
+        // the goal is to unify, but for now this is the "real" list
+        val knownValues = setOf("Melee", "Ranged", "Civilian", "Military", "Land", "Water", "Air",
+            "non-air", "Nuclear Weapon", "Great Person", "Religious")
+        override fun getErrorType(parameterText: String, ruleset: Ruleset):
+                UniqueType.UniqueComplianceErrorSeverity? {
+            if (parameterText in knownValues) return null
+            if (ruleset.unitTypes.containsKey(parameterText)) return null
+            if (ruleset.units.containsKey(parameterText)) return null
+
+            // We could add a giant hashset of all uniques used by units,
+            //  so we could accept that unique-targeting uniques are OK. Maybe later.
+
+            return UniqueType.UniqueComplianceErrorSeverity.WarningOnly
         }
     },
     Unknown("param") {

core/src/com/unciv/models/ruleset/unit/BaseUnit.kt

@@ -493,11 +493,13 @@ class BaseUnit : INamed, INonPerpetualConstruction, ICivilopediaText {
             "non-air" -> !movesLikeAirUnits()
 
             "Nuclear Weapon" -> isNuclearWeapon()
+            // "Great" should be deprecated, replaced by "Great Person".
             "Great Person", "Great" -> isGreatPerson()
             "Religious" -> uniques.contains("Religious Unit")
             else -> {
                 if (getType().matchesFilter(filter)) return true
                 if (
+                    // Uniques using these kinds of filters should be deprecated and replaced ith adjective-only parameters
                     filter.endsWith(" units")
                     // "military units" --> "Military", using invariant locale
                     && matchesFilter(filter.removeSuffix(" units").lowercase().replaceFirstChar { it.uppercaseChar() })