I think you’re going to have a lot better experience with plasma 5.27, they’ve done a lot of bug fixes since 5.25.
I’ve been running tumbleweed for a few years on a few different computers, I’ve only had an issue a few times, but it has a built in method to revert to a save point before the problematic update, so it’s super easy to undo and wait a few days to upgrade again. You can also look at slowroll, it’s tumbleweed on a slower release, though I’m not sure it’s out yet. I definitely recommend it over kubuntu though, I was originally using kubuntu but switched due to wifi driver issues.
If you want to stick to an Ubuntu based system, you could try neon, but it’s built on top of the Ubuntu stable releases so the packages are generally a lot older. It didn’t solve my wifi problems so I gave tumbleweed a shot.