Is it possible to do a one-year course in France as a gateway to find a job there given the difficult job market for a Master's?

Yes, completing a one-year master's degree in France can be a pathway to entering the French job market, even though it is competitive.

After graduating with a master's from a French institution, you may be eligible for the Autorisation Provisoire de Séjour (APS), a post-study work permit that lets you stay in France for up to 12 months to search for a job or start a business related to your field. During this time, you can work full-time without student hour restrictions.

However, finding a job can still be challenging and often depends on your field, French language skills, and networking. Your background in Computer Science and Business Administration, along with extensive work experience, will be a strong advantage.