Early prototype of new Briar Desktop app running on MacOS.
@harald @briar Multi-device support is on the feature roadmap (https://code.briarproject.org/briar/briar/-/wikis/product-backlog). Once the desktop app is production ready I'm sure desktop<->mobile sync will be looked into. The Briar Mailbox app (https://code.briarproject.org/briar/briar-mailbox) looks like it could be laying down some functionality that could be used for multi-device features in the future.
Fosstodon is an English speaking Mastodon instance that is open to anyone who is interested in technology; particularly free & open source software.