You do not type it from a keyboard; you copy it. Press the copy button above and paste it into any app. That is the whole point of Unicode styled letters.
Where can I use the Sans Serif X?
Anywhere text is accepted: Instagram bios, TikTok names, Discord, WhatsApp, gaming profiles and documents. The full Sans Serif alphabet is linked above.
What is the Sans Serif letter X?
It is the letter X rendered as the Unicode character ๐ท (code point U+1D5B7), part of the Sans Serif styled alphabet. It is a single character you can copy and paste anywhere.