RE: routine or Job to renew service contracts that expired
Few things you could tried out here:
1. Set up a view on the service contracts page using date formulas so it is dynamic:

2. Try out the user tasks, this of course takes user discipline

3. Setup a Power BI report using web services to publish the data. The report could then be placed on the role centre. If you are using Power BI pro you can setup alerts on specific measures so for instance if you had a measure of "contracts to expire next month" you could setup an alert whenever it is not 0.
4. Again using a web service to publish the data use Power Automate to review any service contracts that have a date within a certain amount of days. If so send an email or other notification type to a user or collection of users.
5. If you have Jet Reports or another report solution that has scheduling/email capability create a view and have some calculated fields to determine if an alert should be sent.
Plenty of options available other than generating a report in BC itself and having it run on the report schedule feature so it appears in your report inbox. This of course requires development which is more difficult to achieve if you don't have in house skills.