Fail-over or switching the Reporting server database
You can use AlwaysOn Availability Groups to replicate the SSRS Databases to other servers, and reference the Availability Group Listener in place of the server names to allow for failover between servers.

Be aware that Availability Groups do not replicate server level objects such as logins or jobs. If you have any subscriptions in SSRS these will be scheduled jobs that will need to replicated outside the availability group, and you will need to put a mechanism in place to stop them firing when their server is not the primary node.

Here are a number of blog posts that go into further detail about setting up SSRS onto an Availability Group:
https://marcosfreccia.com/2018/06/25/reporting-services-databases-availability-groups/
https://jbswiki.com/2017/09/06/reporting-services-using-alwayson-availability-group/
http://techtalklive.org/ttlblog/making-sql-server-reporting-services-highly-available/