SSIS is not dead, far from it. This article: Dynamics 365: Data Migration with SSIS KingswaySoft and PowerPack is a tutorial showing you how to use this technology and accelerators to facilitate data migration.
Let's see this nice Tips to use PCF for Dynamics 365 On premise v9.1. Indeed, PCF is officially only supported for Online version of D365, but with this quick unsupported tip you could use it either on on premise version.
When developing a Portal with Power Apps Portal, you'll reach a point, where you want to have your developments in a source control or where you want to deploy your portal to a production environment. It's possible with Power Apps Portal source code with Visual Studio Code and Power Platform CLI.
It's always good to use D365 API calls when dealing with Ribbon's rules. But what about long running calls, you have do it asynchronously to not stuck the ribbon load. Let's see this trick about : Dataverse Use Async Promise in ribbon enable rule
Dynamics 365 Developer Toolkit was a very useful tool for CRM developers, nowadays the new Power Platform Tools for Visual Studio will replace it and it's a good news ! With a lot of new features. Come discover it on this article !