Silent Alarm
This app brings up a bold on-screen alert at set times, for those who cannot use a noisy alarm.
Unzip the file and drag Silent Alarm into your Applications folder, then open it. It needs macOS 14 (Sonoma) or later. There's no window or Dock icon — look for a small bell in the menu bar at the top of the screen and click it to set alarms. Try Test Alert to see what an alarm looks like.