2019 Modern Sharepoint List - Totals

Deleted I don't think you will find an out-of-the-box way to configure this. You will probably need to create a PowerShell script as a Scheduled Task on a local server or develop an Azure Function Timer Job. In either case the script/code you write could be scheduled to run on weekends, at the start of the weekend remove all permissions to the list or set them to read-only/view for any groups that have access, then when the weekend is over the script/timer job can set the permissions on the list back to contribute/edit.

Deleted In my opinion the only way to do achieve this globally, is to set all site collections into read-only mode. Though I'm not sure if it's possible to do it via powershell in SPO and how efficient would it be for a large number of sites...