The version string in newer SQL versions includes "RTM" followed by the CU/GDR level when applicable (such as "(RTM-CU24)" in your case). This has been the case since SQL Server 2017 because service packs are no longer used to distribute patches. In SQL Server 2016 and earlier versions, the version string indicates the service pack (or RTM if no SP is installed) followed by the CU/GDR level.
SQServer 2019 version
Avyayah
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Reputation points
After installing sqlserver 2019 applied SQLServer2019-KB5031908-x64 Cumulative path. Executing select @2020VERSION got this output: Microsoft SQL Server 2019 (RTM-CU24) (KB5031908) - 15.0.4345.5 (X64) Dec 4 2023 14:44:16 Copyright (C) 2019 Microsoft Corporation Standard Edition (64-bit) on Windows Server 2019 Standard 10.0 <X64> (Build 17763: ) (Hypervisor) I was not expecting RTM in the version name