- I think Free had it since forever and a half, although IIRC it was some weird 6rd or something. Freebox v6 (2011) for sure had it, v5 (2006) may had supported it from the start and for sure supported it down the road, I think v4 could have had it too through an update at least but honestly can't recall.
- Orange in France had a public opt-in experiment for native IPv6 over ADSL to which I enrolled at the time.
- Then I lost IPv6 because I moved to a cable operator which did not support DOCSIS 3.0 (a requirement for IPv6 on cable connections) at the time.
- After that FTTH rolled out and basically every ISP provided native IPv6 on it from the get go.
Non-biz IPv6 support in France is sitting in the ballpark of 99% these days, both residential and mobile. National regulations helped a lot. Residentially there has been a huge plan towards a national FTTH rollout, including in remote areas (the idea being that no one should be cast aside of a full speed internet); this plan also had specific requirements to enforce competition to prevent regional or local monopolistic situations such as the one that historically happened with cable operators (or like the ones I keep hearing about in the US). For mobile it was simpler: you want a radio license for 5G? you have to support IPv6, or else.
Out of curiosity, what residential ISPs were handing out IPv6 15 years ago?