Lack of discoverability makes your project opaque, even if you aren't doing it intentionally.
Having teams only work in their own silo can cause a lack of transparency within a project
Newsletters won't be read if they are too big
Set expectations within your teams that they are required to produce regular team reports.
Use existing activities (like meeting minutes) as the source for team reports,so they don't become an additional burden
The FSF still sends printed newsletters twice a year, they are well read (based on feedback form readers, and use of a hashtag included on them). Teams are expected to write newsletters articles.
Proposal to have a raffle to give away a prize to people who share your newsletter on social media