Hi @jkachel, sorry to hear you're having trouble!
Let's Encrypt checks against your authoritative DNS servers so typically using an external 3rd party recursive resolver like Google DNS isn't a representative test.
You're the second person today to report these problems with Digital Ocean's DNS servers (the other was here).
Given the above, & the way the error changes from a SERVFAIL to no responses makes me strongly believe this is an issue with Digital Ocean's DNS service. Have you contacted their support? That seems like the best next-step from my perspective.