PTY stands for pseudoterminal, see https://en.wikipedia.org/wiki/Pseudoterminal

I haven't seen this error before, but it is generated by this line of code in libssh2: https://github.com/libssh2/libssh2/blob/master/src/channel.c#L1008

It looks like requesting a new pseudo terminal fails for some reason.

Just a guess: is the system you are connecting to serving a lot of clients? Maybe there are no pseudo terminals left?

Can you have a look at the server logs? Maybe you can find an error message logged by the SSH server.

However, you can currently only find, not replace in multiple files.

Use the menu item Edit -> Find in Files… or Shift-Command-F.

Try a three finger swipe left/right: that's the iOS 13 standard gesture for undo/redo.

I'm working on it. See https://twitter.com/Textastic/status/1240620765420163074

Secure ShellFish might be an option then. It's a file provider for the Files app that connects to SFTP servers. You can open the folder as an external folder in Textastic and changes to files are uploaded automatically. 

Good point. That definitely needs to be improved - also on the iPad Pro without home button.

Hmm, if you save your Markdown files somewhere in the "iCloud" location in Textastic, files are synced automatically across your devices. Am I missing something? 

See https://www.textasticapp.com/v10/manual/managing_files/local_files_icloud.html#icloud for details.

This will be fixed in Textastic 9.0.1.

Thanks for letting me know. I'll look into it.