Arduino Moving from Mbed to Zephyr

I've already run into issues in the past where Arduino libraries and scripts that I wanted to use were written with older architectures in mind and wouldn't compile on newer boards. It was not clear to me from this article but is this going to be another architectural shift/change with similar difficulties for older libraries and scripts?

Interesting they chose Zephyr, haven’t heard a lot of good things about it, NuttX seems to be preferred. Never used them myself but that is the sentiment I get.

Is there a rough equivalent to Arduino in the RISC-V ecosystem?

mbed-os was a cool environment but never took off. zephyr is more mature and has an API in C, the learning curve is a bit steeper though.