It is probably a good idea to mention what Redshift actually is, since it's far from the top result in a search, and a lot of people associate that word with an AWS product by the same name. Wikipedia describes the Redshift you presumably mean as:
an application that adjusts the computer display's color temperature based upon the time of day.
It also mentions that gammastep is a more recent fork, but it has not had any commit activity for 2.5 years, so gammastep might be abandoned as well.
I do too (endeavour os), but I prefer Mint. It just works, and it doesn't break as easily. All my laptops are mint, all my desktops are debian-testing (the most stable rolling release around), and I have one laptop where I play around with other distros for fun.
I usually only use it via command line, but that's disappointing to hear that it's no longer supported. I have used redshift-gtk in the past but I could never keep it functioning for very long, and I prefer KDE. It seems every alternative wants to automate it to synchronize with sunrise and sunset, but 90% of the time I use it is simply because my eyes are already aching. I wish there was another with an easy access on/off switch. The built-in functions require going into settings each time I want to change it and that's just no good.
You can add a taskbar icon for KDE night color. Clicking it opens a panel with a toggle, and quick acess to the full settings page. It should be in the config for the taskbar icon applet.
KDE also lets you set it to specific times if you want, maybe it didn't use to?
wl-gammarelay-rs has worked for me. This is a daemon controlled through dbus, but there are some applets listed in the readme as well as a script in the repo for adjusting based on the time of day.
Use dark mode at night and you won't need Redshift any more. It's only relevant for white screens.
PS: This IS in fact the optimal solution - if not for you then for others. I used Redshift for years, suffering its periodic breakages, babysitting the timezone issue, and it was worth it, because a retina-searing reddish-white screen is better than a retina-searing whitish-white screen. But a dark screen is SO much better for my eyes than either of those. I can't believe I waited so many years to do that and I'm never going back.
Sure, images and video are the exception. But I figure that a redshift app can only help so much when a video suddenly cuts to a picture of a white sky. That's really another problem: choppy contrast. Only solution is to increase ambient light behind the screen.
What setup do you have that actually sets a dark background everywhere? In my experience there are always plenty of programs and web pages that stay white.
So I basically use only terminal apps (black!), a couple of messengers (dark mode) and Firefox. And yes, the problem is the latter. For a couple of years I used the Dark Reader extension. It works, pages look great - BUT! nothing would solve the occasional white flash problem. Last time I checked, it's basically unsolvable by addons. Then I discovered the simple solution: Preferences > Manage colors and override the default colors! It works and it's native! Pages sometimes look a bit ugly but always readable and zero white flash. This is a pro tip that hardly anyone talks about, you saw it here.
Welcome to the dark side ! Once you have seen it, you can't unseen it ! White will always be to bright and your eyes will cry blood on every screen/webpage that doesn't have a dark mode !