I favor this alternative as it is heavily used by other projects like Wikipedia, and allows streaming large files, can use service workers. A stackoverflow answer even mentioned that it’s the fastest.
Promises Full RFC 4180 compliance. Doesn’t have an option to specify encoding explicitly.
Server Side parsing by Python:
I would like to avoid this option, as it would require sending the file to server, which will be a function of the internet speed. User may experience more delay than doing the same task in GTK client.