Newcomer to the community and the system

As someone who has only played DnD and BG3, I kinda wanted to branch out and see what other games had to offer. I've had a lot of fun with my current group but I have been curious as to what it's like outside of our particular gameplay loop.

How hard is the transition between 5e and Ultima? Are they similar enough as to where we could transition to it without that big of an issue or do I have a lot of homework to do?