I don't like Night Light because the minimum filter level ("less warm") is still too intense for me. Increasing the range of the slider in that direction would fix this.

There's also the need to use a schedule, as opposed to simply enabling/disabling the filter at any time. But I noticed I can get around that limitation by setting the schedule from 20:00 to 19:59 and then using the global toggle.

Something broke here, at least on Fedora 32. Activation and deactivation doesn't happen consistently, as if it has lost track of the time of day. I usually have to move the temperature slider back and forth to get it to kick in.

I use something pretty minimal myself: https://github.com/graupe/brownout

Redshift does the same thing and is open source, and there is also a port for Wayland.

I had issues that I can't immediately recall with flux on linux, but redshift + redshift-gtk worked out the box. I had to tweak the config a bit, but once it was set it I never touched it again. One of the only issues with redshift was that if you didn't hardcode a lat/long in the .conf then it would ddos location services.