It’s been continuously improving. There are devices that are a hassle but you’re a lot more likely to have things Just Working compared to a few years ago.

My understanding is that Ampere and others should run perfectly like any old x86 with a normal dist like vanilla Debian mostly due to a lot of hard work from individuals in the wider community.

Much of the time, dtb (device tree) and device drivers are what it comes down to.

For more estoric or finicky hardware, I think the dists with the best ARM support are Armbian, OpenWrt, and PostmarketOS.

Jeff Geerling has been reporting a lot about his experiments. https://www.jeffgeerling.com/

I wrote about getting Debian running on a device based on a popular Rockchip SoC last year. I assume the kernel situation has improved since trixie. https://blog.kumio.org/posts/2025/01/bananapim7-hvm.html