For me, it was perhaps simple-scan, a very simple and efficient GUI to scan documents. I used it with my Brother printer / scanner and it works like a charm. Especially since I do not scan stuff often, so a program with more complex UI would have the effect that I forget how to use it until the next time.
I really like LocalSend as well, but it’s very inconsistent with me. I think it has to do with one device being on a VPN, but I’m not totally sure. Basically I have some “one way” connections where one device can see and send to the one connected to a VPN but not the other way around. Is there some way I can specify LocalSend connections to ignore the VPN? I’m on NixOS and installed LocalSend in my user package declarations in my Nix config.