i started using atuin in my macs a few months ago. Searching in the history for strings containing an @ character did work. Quite some days ago, suddenly typing ALT-L (for the @ character on macs) is taken as the letter l - this happens only within the search function of atuin. Once I escape to normal shell ALT-L is working as expected.
There’s a good chance this is due to the keyboard enhancement protocol being enabled in newer versions of Atuin (this is an extension from Kitty, since adopted in other terminals, that gives us much more info about key input).