Onboard

Onboard is the on-screen keyboard most Linux distributions offer when you need to type by pointing rather than pressing. It reads the keyboard layout from the system and comes up ready to use, which is the right behaviour for a tool somebody may need before they can configure anything.

The layouts, key sizes and appearance are adjustable, and it types into ordinary applications rather than living in its own window. The project moved to a community-maintained repository and is still getting releases, with 1.4.4-5 dated August 2024.

The thing to check before you rely on it is the display system. Onboard is built around X11. Its own documentation describes Wayland support as experimental and points at a separate file of limitations. Linux has been moving to Wayland by default, so which one your chosen distribution runs matters a great deal here and is not something you can tell by looking at the desktop.

GNOME also has its own on-screen keyboard built in, turned on in Accessibility settings. If you use GNOME, try that first and reach for Onboard when you need layouts it cannot give you.