Up-to-date alternatives of rssh or scponly

I recommend to just use the common chrooted internal-sftp that is included with most OpenSSH servers. SFTP clients are available on all operating systems so I do not see any problems with adoption.

You might also want to refer to this other serverfault question to allow SFTP but not SSH to assist you with your setup.

One possibility is ProFTPD's mod_sftp module, which does just what you want (chroot, SCP/SFTP only, no shell).