One document for print and epub: Scene break indicator ("dinkus")

So far I've managed to use a single InDesign document for both print and ebook versions of the same book. The differences are so far only in the frontmatter section and some parent page elements like page numbers, so I hide/show a "Print only" layer and "Ebook only" layer for those elements. Has worked great so far.

But now I discovered that my "clever" approach to a divider between scenes (sometimes called a dinkus) wasn't so clever after all. Avoiding graphics for the ebook (they look terrible in sepia or dark mode), the author (my husband) and I decided to use a simple line. Paragraph rules are ignored in epub, and I was afraid that "___" (a series of underscore characters) might have a slight gap between the characters in some fonts used in e-readers and apps, so I used ten spaces styled as underlined, which looks like this:

But apparently the epub export ignores paragraphs with only spaces, so my nice line disappeared!

So my first question is: Do you think underscore characters would be safe (i.e. smooth with no gaps in standard ebook fonts)?

Second question: If not, do you have a different idea of how to make a line that would show up in epub?

If that's still a risk, the author is happy to go with the traditional "* * *" for the ebook. But that's too dumpy-looking for the print edition. So my third question is: Can you think of a way to have something nicer for print but simple text for epub? I'm already hiding/showing layers, but I don't want the whole book repeated in two layers - not only would it be big, it would risk the content diverging if changes are needed down the road. I know I could do a global find/replace of the dinkus at the same time that I hide/show layers to change book types, but it would be preferable not to have too many steps to switch back and forth - I'm afraid I'll forget, or that a stray character will cause the find/replace to miss an instance. There are already three novels and two short stories in this series, and there will be more in the future, so a simple routine would be best.