I have a question. How do I make an initialism out of a word/phrase with a number?
For an example: Should
Rainbow 6 Siegebe
R6Sbecause of initialism is an abbreviation made of initial letters but
6is not a letter.
It’s perfectly acceptable to use a ‘numeronym‘
numeronym is a word where a number is used to form an abbreviation, such as K9 for canine, or W3 for World Wide Web etc.
Your reference of
Rainbow 6 Siege as
R6S is a perfectly acceptable numeronym.