how can change to spanish that landingpage?
Translations can be added from https://translate.jitsi.org/. I’d check there to see if the strings you want have been translated. After translations have been added there, updating translation files within jitsi-meet is a manual process someone on the team will have to do. The last time an update happened is on November 13. https://github.com/jitsi/jitsi-meet/commit/216782d60690359a380db91cafdd49d96932a0f4. Once the translations are in jitsi-meet, and a new version has been made available, you’d have to update your jitsi-meet deployment.
Alternatively, deploy your own jitsi-meet frontend with the translation file edited yourself. I’m not sure how much complication this would add to your usage though. Here are some links to help if you want to do it: