You could check out https://social.coop/about if you're looking for microblogging.
If you're in Denmark https://ukrudt.net/ and https://data.coop/ run a variety of communication services for members.
Likewise with https://konstellationen.org/ in Sweden.
If you need email there's https://kollektiv.email/.
If you have more organisation-type needs there's https://mayfirst.coop/ and https://commonscloud.coop/
Would be good to make a directory of cooperative digital services providers. Maybe there is one somewhere?
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