Purchased new 9th gen iPad yesterday, only 1/2 of my safari tab groups that show on my MacBook Pro M1 Max and iPhone SE appear on this new iPad. All three devices have been updated to current versions of os/x and iOS. I've done the iCloud sync/no-sync toggle, no change.
I've been using tab groups in Safari since inception, but its not fully baked, e.g., no ability to auto-sort tab group names (why not?), limit of 500 tab groups (not an issue for now), strange rename bug on MacBook Pro (requires 2-3 rename attempts before taking the new name, otherwise reverts to what it was), some new tabs created with + in the group simply vanish, etc. Until recently (this year), Safari memory consumption would exceed 40+ GB and crash, especially when using tab groups (bug apparently fixed by Apple with recent os/x updates).
In any case, if anyone has resolved this Safari tab group sync issue with the iPad, please share!