street parking in France - discs required?

I would contact the Office de Tourisme of any town you might want to visit and ask about the discs. Some locations issue them free to those who ask, some charge a fee, some may only issue them to residents.

The restricted parking locations are typically outlined with blue lines.

For example the Rouen Office de Tourisme is found here: https://en.rouentourisme.com/

You may contact any of the tourist offices in English.

Parking disc- zones (setting a time-limit for parking) are becoming rarer, replaced by paid parking with parking meters in the streets, where you choose and pay for your parking duration up to the time-limit for the location.
In the increasingly rare event that you need one, if your rental car doesn't carry one, have paper and a pen around and leave a note saying "Arrivé à [arrival time]" behind the windscreen.

Blue parking zones may be becoming rare in Paris, but they are all the rage (and increasing in numbers) in the countryside. In cities it always appears like every city has a different system - some use an App, some use the old coin in the slot and a paper ticket, some need a debit card and your car rego number.

It's a lottery, even for those of us who live here.

Thank you - your responses are appreciated. I will reach out to each city we stay in.. and look for lot parking (:

I just got back from France, and saw blue marked spaces everywhere; we were mostly in small towns and villages. There were also plenty of non-blue spaces when we needed to park, and occasionally there was paid parking. Sometimes you'll find a large outdoor lot with paid parking, with the pay machines located in one spot near the entrance and exit. You take a ticket when you enter, then pay based on time when you're ready to leave. And sometimes there is "pay and display" parking on the street.
As to the disque for the blue area, there is a web site where you can get a file that enables you to create one at home. I have the file, but I've never bothered to make the disque.

Thanks - good to know they aren't the only available spots. I've been reaching out to tourism offices. They've been very helpful with maps provided for free parking zones. Awesome!