I can't understand how the community can say Ukraine should surrender to save lives and not become a US puppet when surely they'd just become a Russian puppet instead?

If Crimea from 2014 - 2022 is what being "a Russian puppet" entails, i.e. being Russian citizens, that's a lot better than how being a US puppet goes. Unless you mean western Ukraine since Putin probably does not want to annex it anyway, but we can get some idea of what being "a Russian puppet" by that definition would be from looking at the terms of Minsk II, which seem much less bad to me than being a US puppet.