How much RAM does your setup have? If it has 8 gigs do this:

Open your bitcoin node program on your Umbrel. Next to Connect on the right click the three dots. Click Advanced Settings. Change Cache Size (MB) from 450 to 7000 since you have a 8gb raspberry pi. Click Save And Restart Bitcoin Node. This will assign 7,000mb instead of 450mb RAM during syncing which will allow it to sync quicker. After the node fully syncs you can change it back to 450. It's ok to do this why your node is syncing, it won't restart the syncing process.