I had this same error message (as well as Local couldn’t load the file list! when trying to pull a new site) weirdly only on WP Engine sites. Flywheel sites continued to push and pull fine.
Thanks to this thread I discovered /Library/Logs/local-lightning.log where I saw
{"thread":"main","class":"RsyncService","message":"/Users/jacob/.ssh/config line 2: garbage at end of line; \"#\".\r\n","level":"warn","timestamp":"2023-07-24T21:12:40.766Z"}
{"thread":"main","class":"RsyncService","message":"rsync: connection unexpectedly closed (0 bytes received so far) [Receiver]\nrsync error: unexplained error (code 255) at io.c(226) [Receiver=3.1.3]\n","level":"warn","timestamp":"2023-07-24T21:12:40.767Z"}
{"thread":"main","class":"ConnectManifestWpeService","sentryEventId":"6552717388124a9aa27e22a16cd98858","level":"error","message":"Error creating manifest for WPE Service","timestamp":"2023-07-24T21:12:40.769Z"}
{"thread":"main","class":"ConnectManifestWpeService","level":"error","stack":"Error: rsync process existed with code 255\n at ChildProcess.<anonymous> (%%appPath%%/main/rsync/RsyncService.js:1:1548)\n at ChildProcess.emit (node:events:527:28)\n at ChildProcess.emit (node:domain:475:12)\n at ChildProcess._handle.onexit (node:internal/child_process:291:12)","message":"rsync process existed with code 255","timestamp":"2023-07-24T21:12:40.769Z"}
Helped me discover a line in my ~/.ssh/config that had both config and a comment:
IdentityFile ~/.ssh/id_rsa # set default so it doesn't just use newest
Turns out some programs (like rsync apparently) really need comments to be strictly on their own line starting with # so I edited my ~/.ssh/config and now Local is pushing and pulling to WP Engine again.
# set default so it doesn't just use newest
IdentityFile ~/.ssh/id_rsa