It depends on what you would consider stable. I would install it alongside gnome for now and try it out. You can just leave it on your system getting updates while you use gnome and just pop in every once and a while. It's up to you if you want to enable cosmic-greeter and disable gdm for your login page, but if you want stability, just stick with gdm for now.

COSMIC most of the time and then gnome as a fallback when I run into any temporary issues I can't work around.

I do this with a custom bluebuild image I made that uses ublue (fedora 41) as a base and then added cosmic on top along with some other layers that I need/want.

Even better is that simplelogin was purchased by proton and it being incorporated into the product. Already mostly done from what I can tell. I started with Firefox Relay and if they even give me a reason to leave I'll just switch over to what's baked into proton. There is something to be said for keeping them separate though. If I ever leave proton, having kept the relay service separate would be a big time saver.

You could always give out a relay to your family and friends as well. Both Firefox relay and SimpleLogin have custom domains so you can give you mom an email address like mom@myname.simplelogin.com

Here's how I solved email spam.

1. Create a new email on a privacy focused platform (I chose proton)
2. Sign up for an email relay service (Firefox relay, SimpleLogin, etc...)
3. Only give out your actual email to friends and family and tell them not to share it with others or services without your permission.
4. Change your email on ALL your services to a newly generated relay addresses. Only use relay addresses for any online service moving forward.
5. Monitor the old email for a while to find any important services you might have missed.
6. When you get spam from a relay address, you can decide to use the normal unsubscribe option, or the nuclear disable relay option. That's it.

Bonus 01: since your changing all your services manually, you can decide to delete accounts you don't need anymore.

Bonus 02: each relay is unique to the service so you can tell when a service either got hacked or sold your info.

Side Note: there are setups similar to this for credit cards. I use Wise.com for online transactions with 3 different "virtual" cards that I can destroy if they get exposed.