We start to evaluate Mattermost and I don't find a way to prevent deletion for channels and private groups.Every team member can delete everything. Is there a way to restrict deletion? I did not found anything.
Take a look at the RestrictPublicChannelDeletion and RestrictPrivateChannelDeletion settings in the config.json file.
Documentation on these settings can be found in the docs here: https://docs.mattermost.com/administration/config-settings.html?highlight=restrictpublicchanneldeletion