ScummVM dev here.
Save files between different ports of ScummVM should be directly exchangable, with two caveats:
- Make sure both ports are up-to-date. Occasionally, the save format for the engines change, and old versions will not be able to load saves made with a newer version.
- Saves are usually gzip-compressed. But some ports on less powerful hardware have gzip not compiled in, so you can't load a gzip-compressed save there. The default builds for amd64 GNU/Linux should always have gzip enabled, though. So unless you built ScummVM yourself and explicitly disabled gzip compression, I doubt this is the issue here.
So please, double-check that your amd64 GNU/Linux systems is running a ScummVM version number >= the ScummVM version on your Raspberry Pi. Especially when you're using a ScummVM build from your distribution, it might be severly out of date. Grab one of our official release binary packages when in doubt.
If the issue persists, please file a bug report so this can be inspected properly. We might have messed up badly and broken save game compatibility between ports.
In either case, please consider contacting us directly next time you have a ScummVM-related question. We have a forum and an IRC channel (#scummvm on Freenode). The forum even exists mainly for user support; you are way more likely to find help there than here.