elpa-protobuf-mode 3.21.12-3ubuntu1 (amd64 binary) in ubuntu mantic

 Protocol buffers are a flexible, efficient, automated mechanism for
 serializing structured data - similar to XML, but smaller, faster, and
 simpler. You define how you want your data to be structured once, then you can
 use special generated source code to easily write and read your structured
 data to and from a variety of data streams and using a variety of languages.
 You can even update your data structure without breaking deployed programs
 that are compiled against the "old" format.
 .
 Google uses Protocol Buffers for almost all of its internal RPC protocols and
 file formats.
 .
 This package provides an emacs major mode for editing files in protocol
 buffers format. It features syntax highlighting and auto-indentation.