Came across interesting idea mentioning that in original Hebrew, when we call God is "one" (Deuteronomy 6:4, the Jewish Shema) they use the word "echad" meaning something more complicated than one singular thing, so like the unity of multiple. Other times that word is used is when God created first day and first night, combining them into "one" day-cycle. And also when describing man and woman becoming "one" in marriage.

So it's not so far fetched for some to argue that God is both male and female, similar to Taoism's idea of yin-yang. I personally think they're describing the same concept from different angles. But those Christians believing in the trinity might beg to differ.

I'm not Christian, but I do find studying world religions very fascinating.

Singular "they" is old but has never really been popular.

What are you talking about? People use singular "they" all the time.

Greek and Hebrew definitely do have gendered pronouns. Though Hebrew generally prefers suffixes, they're certainly gendered. Interestingly Greek also has a neuter gender in both pronouns and nouns. A better argument might be that God's gender is self-defined, rather than on a biological basis.