SQL Server 2017 Backup strategy
To start with I do not see any technical issue in your current approach. If I may suggest and if it suits your requirement, since your RPO is 24 hours keep DB in simple recovery take daily full backup and every 8 hours diff backup(optional). The diff backup is not even required but just to give you some restore point in between. Now store these backups locally and also on different server in other DC.
Copy these backup files on different SQL Server in other DC and restore it. So now you have always have a complete data which is less than 24 hours new in other DC. This will meet your RPO but yes you should test this to see if that meets your RTO of 8 hours or not.
The advantage with this approach is its very simple configuration, saves licensing cost of few Windows server. You dont have to worry about complexity of AG, even a new DBA and junior DBA's can work on it easily, etc etc...