not much
With Deb packages you’re safe. With Flatpak I would be a little careful because with Debian apps that have been abandoned get some maintainer love or will be removed, while with Flatpak you can install apps that have not been updated for years, not very often but I’ve seen a few of them. Because of that I prefer to check the Flathub page of a Flatpak app before installing.
I think Kbin development is either abandoned or stalled. Perhaps Kbin fork Mbin supports the same feature ? https://github.com/MbinOrg/mbin
When I first heard of Beeper I thought it was interesting. But reading later that they were buying really old iPhones to jail break them for bridging with iMessage I had some doubts. Now they’re bought by the Wordpress people, who also bought Tumblr, and apparently selling user data to AI.. And from what I’ve read about bridges there is no E2EE with Matrix (what Beeper seems to use) to Signal bridge.
Not sure how well developed this Fediverse interaction between Lemmy-Mastodon is, but can you not reply from your Lemmy account to a Mastodon post ? And please change the broken disroot dot com link in your post into https://disroot.org/ t y