mRemoteNG - mRemoteNG is a fork of mRemote, an open source, tabbed, multi-protocol, remote connections manager.
Lunar.fyi - Control monitor brightness, adapt using the ambient light sensor, adjust volume, switch inputs and turn off displays without fiddling with clunky buttons.
Screens - GNU Screen.
DisplayBuddy - Control the real brightness of your monitors directly from your Mac - no need to touch the buttons on your Monitor.
XwRemote - Multi protocol remote client: RDP, SSH, FTP, SFTP, AWS S3, Azure File, VNC.
Nocturnal - Have more control over your screen at night 🌙