I recently set up Umbrel running on a raspberry pi
and synchronized the block chain on bitcoin core application. I was able to synchronize 100% with Electrs overnight. However, when I try to connect with my Sparrow wallet, there was no connection. I opened another browser window with Electrs and it says waiting for Bitcoin core to finish syncing.
its been about 12 hours since you posted this and I will assume the issue has resolved itself.
Have fun 
not yet LOL
you syncing anything else.
this usually goes away after about 24 hours.
it will show intermittently when you open a browser on its working.
Does sparrow just never connect?
Are you querying a ton of stuff with mempool?
it finally started working…thank you @my_bitcoin for your help