The latest supported SPFX version for SharePoint 2019 is 1.4.1. But I'm not sure what is the first SPFx version that started supporting application customizers for Header and footer. Can someone point me to the information, please?
We are trying to understend if we can develop custom Top navigation for SP2019 using SPFX. I have some douts about it. We are going to target the Modern UI only.