SharePoint Server Subscription Edition (on-prem) REST API call via oAuth

This is a SharePiont Server Subscription Edition on-prem farm. and Extrnal application needs to use data from SharePoint via REST api calls.
Need to setup external application to use SharePoint data from REST api via oAuth.

 
1) What are the steps i need to follow?

2) can this be supported by SharePoint Only App authentication (https://learn.microsoft.com/en-us/sharepoint/dev/solution-guidance/security-apponly-azureacs) for SPSE on-prem?
Any sample REST based API calls to get tokens and call SharePoint would be really helpful.

3) Is it possible to use Azure AD app in for the same? if so how to configure trust between Azure AD and SPSE on-prem farm?