MR144 works for me in resolving the "non-existent service" service error with the keycloak module.
@joseph.olstad thanks for the reply.
This patch to openid_connect didn't apply for me, so I tried using MR144 from https://www.drupal.org/project/openid_connect/issues/3462532 📌 Create and utilise autowiring aliases for OpenID Connect Active instead. That, along with MR43 patch to keycloak did indeed fix the redirect problem, even on alpha6.
I also had to reinstall my local dev site after database migrations didn't work, but that seems to be a problem of me doing this on the same install before. When I started with a fresh install on keycloak 1.8.0 and openid_connect 1.4.0 and then ran the migrations, there were no issues.
Redirect seems to work properly for me with openid_connect 3.0.0-alpha5. But with the new alpha6 that came out in the meantime, I'm getting a new error: You have requested a non-existent service "openid_connect.openid_connect".