Running Electrum apps on an Umbrel setup with a pruned Bitcoin node is problematic. Electrum requires access to the full blockchain to function correctly, and many related services, like Electrs and Mempool, also depend on this complete data set. Users have reported issues with these services when using pruned nodes, as they are unable to sync properly or fetch transactions. While ElectrumX can work with pruned nodes, other configurations may not support it effectively, leading to significant limitations.