In order to properly open meeting links, I believe that Teams needs to register a MIME type of "x-scheme-handler/msteams" rather than "x-scheme-handler/teams".
Currently the Teams client only accepts URIs formatted as msteams://, not teams:// as the MimeType in teams.desktop would suggest. So either the MimeType needs to change, or the Teams client needs to accept teams:// URIs.
See "URI Scheme Handlers" in the Shared MIME-info spec: https://specifications.freedesktop.org/shared-mime-info-spec/shared-mime-info-spec-0.21.html#idm46078813120800
A related question: What is the suggested way to open Teams links from e.g., emails? If the MIME type is x-scheme-handler then it seems that the only way to open Teams from a web browser is to use an extension/addon to rewrite to rewrite https:// to msteams:// in all https://teams.microsoft.com URIs.