For stability, I've always been a fan of just Debian 10. But that doesn't meet any of your requirements.

There is a Debian fork that doesn't use systemd, though I don't recall what it's called or how well maintained it is.

Could always try CentOS or RHEL based distros like Fedora or some systemd-less fork. I'm sure they exist, but I haven't used any RHEL based distros in probably six or seven years and even when I did, it was always for servers and not for desktops. Plus, there is some RHEL organization stuff going on that I haven't cared to follow up on because it doesn't impact me. Not sure what the future of projects based off it hold.

Best suggestion, especially if you have decent internet and a decent computer: Download several distros, load them up in VM's and test them out. Even if you hate Debian, can always install a stable base OS and then just load up the VM of your choice when logging in. Gives you a bit more freedom to test things out before comitting to a full blown reinstall.