The seed picker appears blank for me. See attached screenshot. This started in 1.16.0 and continues in 1.16.1.

The really strange thing is, when my son logs into his account on the same laptop and runs Minecraft, the seed picker has content. However, he says Minecraft 1.16.1 on his iPad also shows an empty seed picker.

I see a related issue MCPE-84668 resolved as incomplete. I'd re-open that one if I could, but I can't, so I'm creating this ticket.

Update 13 July 2020: Today, the seed picker appeared with seeds. There have been no updates. Yesterday the seed picker was empty for me after restarting Minecraft twice, but showed seeds when my son ran Minecraft after logging into the same laptop with his account (and then empty again when I logged in and tried it). But today it's working. I expect this bug is going to be difficult to reproduce.