Most of issues listed here were "inherited" from Qt framework and can't be fixed on app level. Some of them are mitigated by different workarounds.
Linux
- incompatible with RedHat / CentOS
- Wayland is not supported and very likely will not be supported at all (due to its own limitations and poor Qt support)
- notifications are not clickable in most desktop environments
- "show on all workspaces" may not work without "better stay on top"
- "transparent for mouse" may not work without "better stay on top"
macOS
- clock position may be incorrect after screen resolution change
Windows
- "stay on top" very often stops to work and app restart is required to get it work again