Decentraleyes breaks the La Ville à Vélo website
Reproduced on Firefox 86.0 (on several Ubuntu desktops) and on Firefox Nightly on Android (210301)
https://adherent.lavilleavelo.org/collect/choice/63989-u-adhesion-a-la-ville-a-velo works well without Decentraleyes (you can see a list of prices)
With Decentraleyes, there is no list, which makes the page not usable.
It seems to come from https://cdnjs.cloudflare.com/ajax/libs/jquery/1.12.4/jquery.min.js , that is missing in the page.
Manually disabling Decentraleyes for this site is a valid workaround