asteriskify - Linux console password prompt with asterisks
asteriskify | cryptsetup luksOpen ...
Pipe it to anything that receives credentials over stdin, such as cryptsetup.
To switch between clear and asterisk mode, press TAB. To reveal only the last character, use CTRL + R.
Note: Expects ASCII or UTF-8 encoding for asterisk mode
Others may exist, but my quick research only found systemd-ask-password which is unsuitable for my use case (inside a my own minimal initramfs boot image).