Agree with Ashok, you may upgrade from CU14 to CU18 directly.
You need to run PrepareSchema/PrepareAD/PrepareDomain since there are schema updates.
After installing the .Net Framework 4.8, you need to immediately upgrade to the latest CU.
Besides, it is always recommended to have a backup of your server via Windows Server Backup just in case something goes wrong after the upgrade.
And in addition, is there any concern that you don't choose to upgrade directly to CU19(the latest CU version)?
It is suggested to always keep your servers as up to date as possible.
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