Anywhere text is accepted: Instagram bios, TikTok names, Discord, WhatsApp, gaming profiles and documents. The full Squared Filled alphabet is linked above.
What is the Squared Filled letter L?
It is the letter L rendered as the Unicode character 🅻 (code point U+1F17B), part of the Squared Filled styled alphabet. It is a single character you can copy and paste anywhere.
How do I type 🅻 on my phone or computer?
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.