It seems that grid layout of virtual desktops was removed in plasma 5.16. Desktops can now be placed only in a vertical list. The list layout is quite unusable with 10+ virtual desktops. (Virtual desktops are really handy and I can't live without them.)

Is there any way to get the grid layout without downgrading to older plasma versions?
Should I file some sort of feature request in bug tracker?

(I hope this is just temporal change, and desktop grid will be available in the next LTS release.)

Upgraded to plasma 5.17, and found a way to put desktops in a grid. The setting for that is possibly also present in plasma 5.16, but I just didn't realize how to use it properly.