Underline (only) texts on Books on iPad

Hello!

I'm unable to underline (and not highlight altogether) books on my iPad (using the Books App).

I select the text, click on Highlight, then select again, click on Underline, then select again, and click on remove... it ends up removing both highlight and underline. Any recommendations?

I'm able to just underline when reading on my Mac (using the Preview App). But apparently Preview isn't available for iPad.

Thank you in advance,

Eloisa