For your specific use case, I'd say give Lebara mobile a shot.[0]

SIM card is free, you can top it up with a prepaid amount or do a one-month plan without renewing it, and I just checked their T&Cs relating to roaming and they are actually quite generous[1][2].

Besides, their website is (for the most part) translated in English due to their target demographic, so no need for full French fluency here!

Some good info in English on the French telco landscape can be found at [3].

[0] https://mobile.lebara.com/fr/en/

[1] https://mobile.lebara.com/fr/en/international-call-rates

[2] https://mobile.lebara.com/fr/en/terms-and-conditions#section...: See section 2.4.2 (in French unfortunately)

[3] https://en.selectra.info/broadband-phone-france/guides/mobil...

Edit: missing word