Yeah, at the moment I get neither showing up on the forums here when I try to select text within a post, but can get the iOS (copy, paste etc) showing on my own post when under edit, or can get them both showing on other forums, in messages and on other websites.
Something similar came up in another thread last week, but if you don’t get the native OS cut and paste options either it’s probably something different.
If it is the same thing, there’s a workaround: hold on a “like” button until the popup of icons appears, then dismiss it: supposedly this clears the state that’s suppressing the quote menu.
I do notice a few comments at the bottom of the linked thread on the discourse forums about a recent ios change, so possibly that’s what you’re running into.
The user reported it as an Android issue, but assuming the AI analysis later in the thread is correct, it doesn’t sound like the bug is Android specific, so it ought to also apply on iOS. Also, reading the analysis more closely, the reaction widget suppresses all selection behaviour, not just the quote menu. (I just tested that on Android: if you start a “scroll page” touch gesture with your finger on the like button then this disables both the quote menu and native OS select. Manually bringing up and dismissing a like button reaction menu gets it out of the broken state again.) So this does feel to me like it’s probably the same bug.