I wish Signal had a more minimalist UI like Messenger or iMessage, it feels very cluttered with all the full timestamps and multiple checkmarks in each message.

i wish signal allowed for user choice. alas, signal is adamant about being a ready-made product that must serve everyone equally & in the same manner.

"For your security, conversation history isn't transferred to new linked devices." is my main grief with signal. I'd rather have a choice over the ability to move my history to a new device.

Sure you can, it's just not automagic (because your messages aren't stored on some external server, like with other apps). You just create a backup file, copy it to the new device, and restore -- I've moved my history to its third phone now without issues.