Nobody needs to knock the bridge down completely. If several concrete deck sections can be destroyed, the bridge will be totally out of use with repair unviable at least for the remains duration of the conflict. Storm Shadows or ATACMs could do that easily.
Ukraine should attack it. Air defence will not be able to save it from the heavy western missiles. I suspect western backers won’t be so keen though. They’ll say it has too little military value to justify the effort and expense.
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https://english.nv.ua/nation/kerch-bridge-left-without-naval-protection-as-russia-relies-on-helicopters-50466644.html
https://www.independent.co.uk/news/world/europe/ukraine-war-crimea-bridge-russia-land-routes-b2540140.html