Dnscrypt-proxy2 2.0.44 allows one to configure it to drop privileges after binding port 53. However, doing so causes it to fail on initialization. I got a copy of 2.0.45 from their site, and it is able to drop privileges.
A commit references this bug:
Date: Sat Jan 23 10:00:48 UTC 2021
New revision: 562387
dns/dnscrypt-proxy2: update 2.0.44 to 2.0.45
Reported by: Bill Blake <billblake2018 % gmail.com>