I just wanted to point out here because the distinction is kind of important.
There are still a lot of things that are popular in the CSR space that are just based on some very weird architectural choices that do typically lead to worse CWV metrics, worse accessibility etc. Looking at you NextJS and larger React community in general.
However hitting those CWV metrics using a CSR solution, especially one that is just straight up standard web platform stuff such as Lit is not going to be a problem at all and you aren’t somehow improving your SEO simply because you rendered it on the server.
I think there is a misconception here that the CWV metrics are processed in a numerical fashion like 0.2s for LCP is better than 0.3s but there is literally not a single shred of evidence for that nor does it even make sense.
Those metrics are bucketed into 3 categories of good, needs improvement and poor intentionally.
