Last time I used kubuntu ~5-6 years ago and it was pretty buggy. Has that improved? I'm on pop os and would probably just apt install to try it out. Is the kde version on pop os lts buggy?

I can't speak to Kubuntu or Pop OS, but KDE itself is much improved these days. I don't have a high tolerance for a desktop that gets in the way of my daily work, but I switched to KDE on Debian back when 12 was in testing and it's been 99.9% great ever since.

I'm on KDE for the last 2-3 years on multiple machines, and I can't say I spotted any KDE bugs. My system is debian testing + KDE though (and I tried it on Manjaro as well). Sometimes it's not the DE, but the distro they come in. Kubuntu reviews bemoaned regressions, for example - some kubuntus worked well, and the next ones didn't.