Remmina is a remote desktop client for POSIX-based computer operating systems. It supports the Remote Desktop Protocol (RDP), VNC, NX, XDMCP, SPICE and SSH protocols.
Seems to be a trade-free tool. They are very transparent with their data collection, as it is a opt-in model, so you can choose to send data to them to for optimization purposes, but you don’t have to: “When Remmina starts asks the user if she/he wants to share some usage statistics with the Remmina developers. As per the opt-in model (https://en.wikipedia.org/wiki/Opt-in_email), without the consent of the user, none of these data will be collected. Additionally a user can asks, at any moment, that any data linked to his/her profiles to be deleted, and he/she can change the Remmina settings to stop collecting and sharing usage statistics.” (https://remmina.gitlab.io/remminadoc.gitlab.io/remmina__stats_8c.html#details)