I’ve got a 2017 MacBook Pro with a dead screen, dead keyboard & trackpad and no battery sitting behind my sofa, closed in a vertical stand and running macOS as a test server. Open Core Legacy Patcher will allow you to boot without the CPU slow down: https://dortania.github.io/OpenCore-Legacy-Patcher/
I have the same device, did you just remove the battery after installing opencore? last I tried, I got omarchy running on it but now it just boots to the startup disk always. Not sure what's wrong.