Glow squid appear to be spawning plenty, however normal squid aren't spawning at all for me, the biomes I'm searching in for squid we're originally loaded in 1.16.5 and the world was created in 1.14.2, If I load up a brand new world squid spawn as normal.
World: https://drive.google.com/file/d/1BB9rc0FAmhbDqrFuOO9cYFUioJoviEiv/view