Simultaneously active dual sims (e and / or physical) have been a bit complicated / unsatisfactory in their management as seen here, for example: Dual-SIM Issues: No way to individually manage mobile data and roaming settings?
To your issue, are APN settings confirmed correct for both? I am actually not well versed in dual SIM management, I do have 2 SIMs (both physical, no eSIM) from different networks (second one for testing) but my regular phones don’t have dual phsyical SIM slots. I see I may be able to test with a OnePlus Nord N20 or N30 as both of those seem to possibly support dual physical SIMs. I’ll put that on my “to check list” so I can at least test dual SIM usage.
With Discourse (at least on desktop) if you just hilight part of a post then you can hit “q” but also an overlay should pop up that allows you to “quote”.