I have this row, where the content highlighted in red is searchable. I expect it always to be visible, but we have some corner cases where this content can be quite long and hidden behind ellipsis (css line clamped). However, we need this data to be present too, so I considered using tooltip for the rest of content hidden behind ellipsis. Do you think it's a good idea or there are some other ways?
I would avoid tooltips for lots of reasons. In your case the main reasons would be:
There would be no way for users to know how to reveal the content. They shouldn’t have to hover (and wait) for a tooltip to (maybe) show.
It wouldn’t work for people without a pointing device like a mouse or trackpad. They wouldn’t work for keyboard users, screen reader users and users who use voice commands.
Generally they’re just not that easy to use.
In your case, I’d suggest a ‘Show more’ button that reveals the rest of the text and can be toggled on and off.