Linux
RetroArch's Linux builds have Cloud Sync since 1.19. Point it at SaveSync and your desktop shares saves with your Steam Deck and handhelds.
org.libretro.RetroArch): config in ~/.var/app/org.libretro.RetroArch/config/retroarch/.~/.config/retroarch/. Older distro versions may predate Cloud Sync; it needs 1.19 or later.https://savesync.fastwater.app/saves/, with the slash at the end, then enter the Username and Password from SaveSync.cloud_backups folder before it overwrites or deletes it.RetroArch syncs saves by their path inside its saves folder. Two devices only share a save when the path matches, so check these settings in Settings, Saving on every device:
The game's file name matters too: Pokemon Emerald (USA).srm only matches a ROM with the same name. Rename the ROM on one device if they differ. Use the same core for a game on each device as well, since a core's saves sit in its own folder when sorting by core name is on.
RetroArch syncs when it starts and when you close a game, not while you play. Close the game before you put a device down, and let RetroArch start on the next one before you load the game there.
If two devices change the same save between syncs, RetroArch skips that file and says "Cloud Sync finished with conflicts". To keep the copy in the cloud, delete the save on the device and sync again (in Settings, Saving, Cloud Sync, Sync Now). SaveSync keeps the 20 newest versions of every save either way, so you can restore one from the dashboard.
Typing a URL and a long password with a controller is slow. Instead, with RetroArch closed (it rewrites its config when it quits), open retroarch.cfg (~/.config/retroarch/, or the Flatpak's folder above) and set:
cloud_sync_enable = "true" cloud_sync_driver = "webdav" webdav_url = "https://savesync.fastwater.app/saves/" webdav_username = "savesync" webdav_password = "<your SaveSync password>" cloud_sync_sync_saves = "true" cloud_sync_destructive = "false"
Not sure where the file is? In RetroArch, Main Menu, Configuration File, Save Current Configuration shows its path.