Just joining the crowd...
Same issue for me - app freezes after opening. iPad 5th Gen, iPadOS 14.3.
The temporary workaround (disconnecting from the internet before and during use) seems to work.
Thrilled I can still use the app for now, but if this freeze happens because of some sort of authorisation call to a server, what happens when the app hasn't phoned home for a few weeks? Many apps allow offline use, but only for a set length of time before they stop functioning. After that they won't launch until they can refresh the authorisation online. Hoping SampleTank isn't one of those
Have submitted a ticket to Support.