Ubuntu 25.04+ replaced GNU coreutils with uutils coreutils, a Rust-based
reimplementation of Unix core utilities. These are different projects
with the same package name:
- GNU coreutils 9.x (C) - Ubuntu ≤24.04
- uutils coreutils 0.x (Rust) - Ubuntu ≥25.04
The uutils comm doesn't recognize sort output as sorted, causing
"comm: file is not in sorted order" errors.
Replace comm patterns with:
- grep -vxFf for set difference (lines in B but not in A)
- sort | uniq -d for finding duplicates
These alternatives don't depend on comm, ensuring compatibility
with both GNU and uutils coreutils.
504ccc45d2