If you dig deeper, you can easily find that the consensus among IT security experts is Signal for privacy / security. Matrix is interesting and I hope it will

If you dig deeper, you can easily find that the consensus among IT security experts is Signal for privacy / security. Matrix is interesting and I hope it will catch up eventually, but currently it is not E2EE by default and it leaks way more metadata than Signal. These point make it strictly worse than Signal for 1:1 IM. The advantage of Matrix is in federation, but regarding privacy / security, it is still behind (much to my regret). Other apps that could provide similar guarantees in theory are less used and have received less scrutiny, so more not yet exposed bugs and design flaws should be expected. Other apps have been relatively well studied, but have well-known design flaws that also make them worse than Signal (WhatsApp and Wire leak way more metadata).