Turn your phone into a powerful Bluetooth keyboard and mouse

https://lemdro.id/post/131133

Turn your phone into a powerful Bluetooth keyboard and mouse - Lemdro.id

This is a gem if an app that turns your android phone into a Bluetooth mouse and keyboard for other devices. I use it to control an Android tv box. As you no typing with on-screen keyboards is an absolute pain. With this app you can type anything on your smartphone and send it to any text field on your other device. You can also add cistom keys and key combinations. It can also work as a mouse with customizable buttons.

As an alternative, you could consider KDE Connect. It does a lot more than just keyboard and touchpad. You can even send files both ways extremely quickly.
It looks like you have to install KDE connect on both devices, and they have to be on the same network. Handy, but completely different type of app and method of execution.
Yeah this app needs no “server” app. It’s original names was “serverless keyboard and mouse”