Good morning, my name is Ryan Eaton and I've been playing Minecraft: Java Edition for almost 11 years now! Throughout my time with the game, I have created some pretty cool things. Here's one example, I did the datapack and resource-pack design: [login to view URL]
For the portal, I find it quicker and efficient to work with Datapacks. Depending on your portal idea, I definitely can replicate the functionality with a vanilla Datapack. This is good for clients because it's quicker and easier to develop, and can be modified easily (even by clients) later on since the code is Minecraft commands in files. Several previous Minecraft-related clients who were initially asking for a mod or plugin were very happy to switch to a Datapack when I explain the pros and cons to them.
Anyway, please send a message with some more details about the project, as I'd love to work with you in my favorite game!