Or is there a decent tracker list like DDG's I can import into the JS blocking settings in some way? In want to harden Ungoogled Chromium as my backup browser.
Well they always need some maintenance since things tend to change, especially in browser development. I don't know if uMatrix is flawed in some way but maintainer of uMatrix archived repo on Github with last commit on April. I also used uMatrix but I recommend using some other alternative such is NoScript