When I started getting reports from customers on my company's website about issues, I was baffled for a few minutes because all my tests with OpenSSL and cURL, etc. were passing...on my Arch Linux install. Then I switched over to my MacBook and ran the official /usr/bin/curl version (instead of my brew install curl version) and I understood what was happening. Gotta love when this happens.
My guess is openssl, since we experienced this problem with a lot of our internal services and our monitoring, both of which make heavy use of Perl and LWP::UserAgent, which build on OpenSSL. CentOS 7 boxes had problems (easily shown through the lwp-request util, which can often be used like curl's CLI tool), but not on CentOS 8.