When placing the order, you get a funny text string from the ACME provider. You need to create a TXT record that holds this value. How you create the TXT record is up to you and your DNS server – the ACME provider doesn’t care.

I don’t believe DNS-over-HTTPS is relevant in this context. AFAIK, it’s used by clients who want to query a DNS server, and not for an operator who wants to create a DNS record. (Please correct me if I’m wrong.)