I have lived in France for over 20 years. I live in the department of the Drome, my prefecture is at Valence.
When I first came to France it was still normal if not required to have a Carte de Sejour, so I had one in the past. I think the last time I renewed it at the local Mairie was in the early 2000's, in those days if was for 5 years if my memory serves me well...
I stopped renewing the Carte de Sejour when it became a requirement to go to the Prefecture, and under European rules it was not longer necessary.
Applying for a Carte de Sejour had always been simple as I easily satisfy all the requirement. French tax returns going back years..
With Brexit, last year I decided to apply again for a Carte de Sejour. This time the process was difficult, more complicated, time consuming and unpleasant. I needed to contact the British Embassy, MPs, MEP's and the labour party for help. The process took 10 months in total.
Each stage requires that you go to the Prefecture, about 2 hours each way. They refuse to make appointments, so you have to go and queue. Normal waiting time is about 1 to 2 hours. So it is at least half a day for each visit.
The first response from the Prefecture was that they would not process my Carte de Sejour because I am British, and they were waiting for instructions from their Minister on Brexit. They also said it was not necessary to have a Carte so it was a waste of their time. Then they required documents they had never required before. A Birth Certificate that was translated by a Court approved translator, proof of income, 5 years tax returns etc. They eventually agreed to process my request. Under their own rules they have to take no longer than 6 months to process if from accepting all the papers, they took 5 months 3 weeks. I was then summoned to go to the Prefecture to collect the Carte de Sejour. So 10 months after my first visit to the Prefecture I finally had a 10 year Carte de Sejour.
I would add, that they wanted to issue a 1 year Carte de Sejour, I had a considerable argument about that with them.
So all in all a very time consuming, difficult and unpleasant process.