Polytonic Greek on ios 14 keyboard

I tried to add the polytonic Greek keyboard which employed in ancient Greek language. Its writing system contains special diacritics e.g. iota subscript, rough/smooth breathing, long vowel mark, etc.

As following several previous related questions that asked and solved in this Communities, it has no any additional alternatives or, even, an arrow on the edge of the Greek tab. I, so, have been still unable to add the keyboard onto my iPad yet.

Please note that most of those questions were asked before iOS 14 was launched.

Therefore, is there any way to add polytonic Greek onto iPad?

Thank you.