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It's your case. I just got a s21 ultra and tried 3 cases, the speck presidio2, the spigen thin fit and rugged. They all fit easily with about 1/2 to spare vertically, but you do have to put the top in first.
If not, the charging pads underneath are quite standard, so may be it would be possible
to swap the version with two portrait mode with one providing two portrait mode and one lanscape mode.
There are plenty of the older Model 3 Jeda charging pad on e-Bay that could possibly used instead.
This might require a little bit of handy work but should not be difficult to do.