Extensions for Safari on iOS and iPadOS have been available since 2021, I’ve been using ad blockers on those systems, but it’s nice the have uBlock now.
Trying to actually write one before, it's incredibly frustrating experience, as you still need to have some weird native glue code in in Swift/Obj-C. And everything is under-documented, as it the true Apple Experience. (I forgot the details. I can find the code on github, maybe.)
If you ask yourself why there are so little Safari extensions, this is why.
edit: I look at the code now... I needed to wrestle with BOTH cocoapods and npm, at which point I gave up
in my repo. Then I opened xcode, configured the signing/capabilities, and built it. IIRC I had to create the directory for the output because xcode didn't do it itself, but once that was done I could install it to both macOS and iOS. Honestly I was surprised it was so little effort. I don’t doubt that an extension with more functionality than mine might require a jumping through a lot more hoops, but it definitely can be easy to successfully target Safari IME.