PARIS, June 18 (Reuters) - Carmaker Renault (RENA.PA) has signed an agreement with French trades unions that will allow thousands of its staff to work from home for up to three days a week, the company said on Friday. The new workplace arrangements will be rolled out in several stages, starting in September 2021, Renault said, adding it would offer support and training on how best to work remotely. The hybrid system will be voluntary and based on two days of working from home per week, with an additional day at the manager"s discretion, Renault added. The company expects 20,000 staff in France to be eligible to take up the offer of remote working which will cover most roles apart from front-line production. Rival carmaker Stellantis (STLA.MI), the maker of Peugeot and Citroen cars, has agreed similar arrangements with its French workers. The future of the workplace is being heavily debated after the coronavirus pandemic forced the closure of many offices and showed how many tasks could now be performed by staff from their own homes.