How to have an invisible/blank/empty Twitter name in 2021?
Twitter does not allow you to set your Twitter name to an invisible/blank/empty message using regular spaces. They even have a detection for special non-space characters like U+3164 HANGUL FILLER.
A blank Unicode character that still works in 2021 is U+1D159 MUSICAL SYMBOL NULL NOTEHEAD which looks like a regular space character, but is not detected as one by Twitter. Just copy the character using the following "Copy" button, and paste it into the "Name" field of Twitters edit profile page:
Voila! Now, you have an invisible, blank, empty Twitter name!