LUKS does not present a graphical prompt - plymouth is capable.
Is the prompt looking like the prompt pictured in this topic?
→ [root tip] [Utility Script] Encrypted Manjaro Linux using Verified Boot
If yes - what is the version of plymouth on your system?
pamac -Qi plymouth
Plymout exist in two versions - one with stable and testing - and a newer in unstable and upstream
$ mbn info plymouth -q
Branch : archlinux
Name : plymouth
Version : 24.004.60-8
Repository : extra
Build Date : Sun 07 Jul 2024 19:11:32
Packager : Balló György <bgyorgy@archlinux.org>
Branch : unstable
Name : plymouth
Version : 24.004.60-10
Repository : extra
Build Date : Sun 07 Jul 2024 20:12:55
Packager : Mark Wagie <mark@manjaro.org>
Branch : testing
Name : plymouth
Version : 22.02.122-18
Repository : extra
Build Date : Tue 07 May 2024 16:47:12
Packager : Philip Mueller <philm@manjaro.org>
Branch : stable
Name : plymouth
Version : 22.02.122-18
Repository : extra
Build Date : Tue 07 May 2024 16:47:12
Packager : Philip Mueller <philm@manjaro.org>
Did you attempt to disable plymouth and remove it from your system ?