Unlike some other solutions, Warp is simple, focuses only on sharing a shell session, and does not require ssh or a central server (sort of). Despite not using ssh, the connection between machines is secure. However, if you are really worried about security, note that the session name (which is not published) is all anyone needs to connect. Probably should make it hard to guess.
On the other hand, by default, people can only view your screen session, so at least an attacker can’t just start entering malicious commands. You can, however, authorize someone to take control, but in that case, you would want to be very sure you knew who you were allowing to use your computer.
Go will run on the Raspberry Pi, so it should be easy enough to install there. You do need at least version 1.7 of Go. You also should have the GOROOT and GOPATH environment variables set. You’ll probably want to add your GOPATH to you system PATH, too, to make it easier to run warp (and other Go executables).
Although the README says there is no central server, it does look like it uses the warp.link server to manage connection requests. We aren’t Go experts, but we assume an examination of the code would see the warp.link server resolving names and handing off the connection. But if you are really security conscious, you should probably make sure.
If you don’t mind ssh, you can always use this fork of tmux. You can also use tmux or screen directly (see the video below). None of these methods are going to be as robust as Mosh, but then again that’s a different use case. Or you can just give someone the keys to your computer if you dare.