This just stopped working for me. "Can Evolve" used to show a number under it but now it doesn't and when you click it, it shows all your Pokemon. So they've borked it somehow.
Strange how it took a week longer to break for me than you.
Is there a workaround?
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The “Can Evolve” search filter does not function.
Issue description: The “Can Evolve” search filter does not apply when selected.
Issue status: Resolved in upcoming release (0.219.1). In the meantime, we have removed this option from the Recommended filter list to mitigate confusion.
https://niantic.helpshift.com/a/pokemon-go/?p=web&l=en&s=release-notes-known-issues&f=known-issues