I'm thankful that I don't work on projects that have SEO needs. SSG (for JS frameworks specifically) feels too unstable for me. I get the value, I understand why people need to do it, but it just makes everything more complicated. Also, I'm not sure if you can have an offline site with SSG? They might be compatible but I'm not sure. I know some SSG is essentially "SPA with the first page rendered already" so maybe that can work offline?
I looked at InertiaJS and it feels like too much "magic" for me personally. I've never used it so I could be wrong but it feels like too many things you have to get working perfectly and the instability in the JS ecosystem makes me worry about adding too many layers.
What's SSG?
Tangential but I noticed a certain common conflation between pre-rendering and server-side rendering. Very often plain SSR is all it takes for good SEO performance, SSR in this case simply being rendering the page on-demand before serving it to the user.
Pre-rendering (as popularized by static site generators) is the additional step that increases complexity significantly, sometimes security issues too when session-protected cached pages are mistakenly served to the wrong users.