We are trying to deploy the ArcGIS Enterprise without web adapters since we have a third party load balancer F5
Q1. Does ArcGIS Enterprise work without Web adapters in DMZ zone? if yes
What type of authentication should use in order to be able to access esri mobile apps suchas Survey 123
I would take a look at this documentation: https://enterprise.arcgis.com/en/server/latest/deploy/windows/multiple-machine-deployment-with-third...
Yes, Enterprise, (specifically Portal and Server), will work without the web adaptors where requests are routed from your load balancer or reverse proxy directly to Portal or Server. The web adaptors are only required if you want to use IWA. Survey123 and any other client applications will with any authentication currently supported for Enterprise, (IWA, SAML, portal tier, built-in, etc).