Theres a bug since a recent update that the system monitor dosent show the column names ill attach image for refrence
Yes this bug is known and fixed in plasma 6.7
A fix has been backported: upgpkg: 6.11.1-2: Fix QML TableView regression (47537176) · Commits · Arch Linux / Packaging / Packages / qt6-declarative · GitLab
Confirming that the 6.11.1-2 update for qt6-declarative has officially fixed the issue on my end. System Monitor column headers are back to normal now after a reboot. Thanks for the quick backport!
6.11.1-2
qt6-declarative