So, I will go by the list of mods I tested Battlerods on before this release:

-Thorium (Alone and with Thorium Bosses Rework)
-Calamity (alongside Clamity, Catalyst & Hunt of the old God, Older Wrath of the Gods worked, have not tried the most recent version...)
-Homeward Journey
-Mod of Redemption
-Martin's Order
-The Stars Above
-Vitality Mod
-The Galactic Mod
-Fargo's Souls Mod
-Storm's Additions Mod
-Stellaria Mod
-Exxo Avalon Origins
-Uhtric Mod
-Forgotten Evils
-Alchemist NPC
-Fernium Mod
-Spirit Mod
-AvasMod
-Cerebral Mod
-Cal's Content
-Remnant Of The Ancients
-Infernus Mod
-Aequus
-Starlight River
-Qwerty's Bosses and Items
-Edorbis
-Consolaria
-United Collection
-Vibrant Reverie (WIK's Mod Redux)
-Gerd's Lab,
-EXCELSIOR
-Secrets Of The Shadows
-Valhalla Mod
-GaMeTerraria
-Rothur Mod
-Echoes of the Ancients
-Clicker Class
-Bombus Apis
-Paracosm
-Spooky Mod
-Zylon
-Gensokyo
-KagMod
-Ebonian Mod
-Hijinks
-Lost Port (had some issues but unsure if it was the Ultramodded runs fault)
-Parakite Mod
-Verdant
-Elementalist and Tyranny

They were not all tested at the same time, many were in Ultramodded runs, some were just classics I always play with (Shout out Thorium), but regardless most went without issues and their pre-moonlord most bossfights tended to be about 2 minutes which is an upgrade from the 5 to 10 seconds some used to take.