K2 gives error when used with kotlinx-serialization. But AFAIK, for the frontend, it only adds some minor diagnostics that I'm fine without. So could it work otherwise?

Yes, we didn’t expect that 1.7.0 or .10 works with any of compiler plugin. Some of plugins are planned to be supported in 1.7.20. So it makes sense to try K2 with turned off kotlinx-serialization. Just make sure that the build is also passed in case of K1.

Yes but I mean, those plugins are mostly about IR (backend). So would it be possible to disable the frontend part and use them with K2 right away?

сс @mglukhikh @dmitriy.novozhilov

Even IR plugins are sometimes written with frontend-specific code (using descriptors, binding context, etc.), so it's quite possible they will not work with K2. In fact, now we are supporting plugins case-by-case. Serialization plugin is expected to be available in 1.8.0. In 1.7.20 we support allopen, noargs, lombok, parcelize, sam with receiver, atomicfu.