According to the following LINK (see quote, there is a link in it), the SNCF might go on strike on June 22 and 23! (Q: Do they announce their strikes 3 months in advance??? 8) )
(short resume: the railway workers want to go on strike 2 days per week for about 3 months, to defend their status as railway employes)
IF this is true, this will most definitely have an impact on those who arrive either by plane in Paris (CdG/Orly) and want to travel by train. Either look for alternatives, or try to get a flight to Nantes after it. (if this is possible) FLIXBUS (long distance bus) is also active in France, check their website. ([url=https://www.flixbus.fr/]www.flixbus.fr, where .fr can be replace by any other country code if desired)
Once again, much can change in 3 months! But better be prepared! Better safe then sorry!
Additional info: unfortunately, this strike is still an issue in France.
For all information about your train journeys in France, BEFORE YOU ARRIVE THERE, can be found on https://www.sncf.com/fr/greve-nationale/la-circulation-des-trains-peut-etre-pertubee-aujourdhui, but unfortunately, the English site seems to be out of order. (I do not know for the German part, which is the last other language you could use)
Keep in mind, STRIKE will be (if correctly informed) on FRIDAY June 22 and SATURDAY June 23! So if you arrive earlier, say Wednesday, or Thursday, this should NOT effect you. Nor should it effect you on MONDAY, June 25!
All info can be found on SNCF.com and all other (usual) channels on social media. (if you have any)
We stay in Nantes and take the train each morning across to Clisson. Does this mean non of the trains will be running? Or will the local trains still run?