Where the Letter L Breaks the Pattern
Most mathematical styles run A to Z in one unbroken block, but not all of them for this letter. Script capital L is â (U+2112, Script Capital L). It was added to Unicode in the Letterlike Symbols block years before the mathematical alphabets, and the later block left a gap there instead of duplicating it. On some devices a different font draws this character, so a word set in that style can show one letter that looks slightly unlike its neighbours.
Small Capital, Turned and Other One-Off Forms
Small capital L is Ę (U+029F). Like most small capitals in Unicode it was encoded for phonetic notation, not as a font feature, which is why small caps text pastes as ordinary characters. Upside-down text uses the turned l, ę (U+A781). Superscript l is ËĄ (U+02E1). Subscript l is â (U+2097). The regional indicator ðą is half of a flag: two of them in a row turn into a flag emoji when they spell a country code.
Which L Is Safe to Paste
Bold ð, italic, sans-serif and monospace forms display on nearly every phone and computer. Circled â and fullwidth  are also widely covered. The squared and dark squared forms of L have no emoji version, so they stay black and white. Screen readers may announce a styled L by its full Unicode name or skip it, so keep anything important in plain letters as well.