It obviously can. My first sentence was "uBO already runs on iOS." You asked if Orion was compatible with "normal desktop Firefox and Chrome extensions." There's no distinction between desktop Firefox extensions and mobile ones! Addons on both are just standard WebExtensions, and I've already noted that it runs both Chrome and Firefox extensions.
Your lack of understanding of what browser extensions are is exactly why it would be better if Apple explicitly banned browser extensions from the App Store. Ignorance is a malware vector, and even you, a commentator on Hacker News, do not understand the browser extension ecosystem. Instead, they're taking a bunch of flak for something they aren't even doing, all the while iOS has had a browser supporting uBO for years.
"I noticed similar issues. I think the reason is that Orion on iOS supports fewer Web Extension APIs than it does on desktop (see the list below). As far as I know, uBlock Origin makes heavy use of the webRequest API, and this seems to be mostly unsupported on iOS. So I decided for me to use uBlock Origin only with the Mac version and rely on Orion’s built-in content blocking on iOS."
"When using the uBlock Origin browser extension on iPhone or iPad, it is unable to block any ads or trackers on webpages. The displayed interception count always remains at 0. This result is consistent whether downloading the version from Chrome or Firefox's software store."
Sounds like from that (may be out of date, some posts complaining are 15 days ago though), it runs but doesn't work:
