How to survive the battlefield

[Fynneberg]

Does anyone have a perfect build/setup to beat it? Tiny rooms, a maximum of 2 boxes for coverspawn and the enemies destroy cover with one attack. Please someone share their eldritch knowledge with me because my smoothbrain can't come up with a functional strategy.

[Mr. No_Effs_Given]

I just cheesed all way through, shooting enemies outside the rooms. The mortar enemies are ridiculous, even with cheese they are very annoying to deal with it. I already beat the game several times (including true ending), and even the last boss is easier than these guys.