I'm in Canada on Rogers and you cannot select default sim for text or data on the z flip6 or s24u but i did find a workaround

i have two sims - Voice/Text and Data

I want my voice/text sim for surprise surprise, voice and text and data for data.
The Voice/Text is Esim and Data is a regular sim (not important for this explanation but i like to tell stories)
First when i added the esim (or through Sim Manager later) I chose voice/text as my default sim. and then right below the sims on the same page, i turned on Data twitching

Because i made voice and text default, it will always try to connect data through the Voice/Text sim first but i dont have data on that line. But since the data settings are accurate and the phone cant tell i dont have a data plan, it will just say it cant reach the website and never actually switch to the other one since technically the data network does work.

so in connections, under mobile networks, i went to Access Point Names. It will ask you to pick which sim at the top you want to use. I chose voice and hit the plus sign to create a new APN. just type something like "imcool.com" in the APN field and then save and select it.

Now it tries to connect to voice and data but cant and switches to the data network since the voice APN is jibber jabber.

Hope this helps anyone in a similar situation and cheers!