Thanks so much for this, explains Umbrel very well.
I was also seeing this issue; the lost connection happened about once a day for me. I contacted support and received this response:
"This is likely related to a networking issue that we have found is affecting a small amount of users. To fix it, can you please try these steps here:
Navigate to Settings (http:umbrel.local/settings) > Advanced Settings > Enable the Beta updates program. You can then close that module and select ‘Check for update’, please then update to umbrelOS 1.2 Beta."
I’ve performed the upgrade and will keep an eye out for the issue. If it still comes up I’ll post an update here.