Sites/platforms that curate lists of publishers.

The Submission Grinder (https://thegrinder.diabolicalplots.com/) - Completely free. Kept purposely "old school" (or "retro," as the kool kids call it).

Chill Subs (https://www.chillsubs.com/) - Free, but with a subscription level that opens up more features. Modern interface.

Duotrope (https://duotrope.com/) - Subscription based with a free trial period. Modern interface.

And some others I've dug up as well:

Poets & Writers (https://www.pw.org/small_presses)

Submittable (https://manager.submittable.com/opportunities/discover)

Driftwood Press (https://www.driftwoodpress.com/submission-opportunities)

New Pages (https://www.newpages.com/guide-to-magazines/literary-magazines/)