If you have a Umbrel Home, in theory and according to what they promise, you can use an external disk as storage without problem.
Now, All depends on your needs and the apps you use.
For example, in my case, I installed Bitcoin Core to run on disc 1 and put the blockchain on disc 2.
To achieve this, it cannot be done with a simple click as those of the Umbrel promise. You have to make some nodifications in the configuration.
If you are interested in the topic, I documented it in detail: HOW-TO Using 2 SDDs in umbrellos (in a simple and practical way)
And it could not be wrong to take a look at a mini manual of good practices that still is still in force with the most recent version 1.4: umbrelOS- Good Practices