Welcome @mnqn!
E. g. see thread_1 and thread_2 for some discussion on this:
If your boot partition is encrypted (as part of a full disk encrypted setup), at this early stage in the boot process, there is only grub to unlock the drive to get to the initramfs and kernel. So AFAIK, no, there’s no way for plymouth to inject itself before the actual filesystem is unlocked and therefore no way around grub’s textual password prompt.
In case of an unencrypted boot partition or if you want a nicer appearance after the initial grub unlocking, you could try installing Plymouth.
Plymouth provides a graphical boot animation while the boot process happens in the background. Afaik, this is what Pop_OS! currently uses and therefore exactly what you’re looking for.
I don’t have any experience with plymouth and therefore can’t help out there.
[Edit] Regarding general (not encryption!) password asterisks, see here for example. I would personally advise against them though.