The following formula will return the closest moon phase emoji in Excel:

=LET(phase,MOD(ROUND(MOD(NOW(),29.5275)/3.691,0)-2,8)+1,UNICHAR(127760+phase)))

Good news! According to Swift Package Index [0], Tiny Moon is already compatible with Linux environments.

0. https://swiftpackageindex.com/mannylopez/TinyMoon/