Thanks for the upstream check. I'm also subscribed to https://github.com/haproxy/haproxy/issues/1276, let's see what they say. I noticed that the build has a lot of deprecation warnings coming from openssl3, but as long as they are just deprecation warnings (but still work), it should be ok.
- Bug#1006007: haproxy: FTBFS with OpenSSL 3.0 Sebastian Andrzej Siewior
- Bug#1006007: Andreas Hasenack
- Bug#1006007: Vincent Bernat
- Bug#1006007: Andreas Hasenack
- Bug#1006007: This appears to be a duplicate Tim Düsterhus