Message history is a valid point. Signal just announced they’re fixing it.
Safety number change notifications are probably necessary to maintain Signal’s high level of security. The above device linking improvements should make them less frequent, though I’ll concede some might consider that a worse UX than an insecure chat with no such notifications.
Preferring websites to apps when possible makes this approach more effective. If you use apps with ads in them, they will likely get sensitive information as described in the article.
System wide ad blocking helps more. Private DNS is the easiest way; Mullvad provides a free option.