What is the best way to write a client-server application for old computers?

Question

Programming

There is a park of old computers with 512MB of RAM, single-core CPUs without SSE2.
It is necessary to write a client-server gui application for simple work with the database.
Due to the lack of SSE2, python3, golang immediately disappeared.
There are thoughts to write in Qt, C # or, in extreme cases, in php (work through the bowser).
I want to learn along the way a developing language that will come in handy in the future.

Answer 1

If a DB on the same iron - that it should not be any client-SERVER.
What bothers you to recompile Python or Go without SSE support?