One repo => two netlify sites based on netlify config?

I have a single React repository and want to use it to make two different websites. I can control a lot of variation between the two by setting REACT_APP_VARIABLE environment variables with netlify, but I can’t vary the state of <head> that bots see. I want each site to have unique og and favicon values. So I was thinking I could create index_1.html and index_2.html files and configure service of one or the other using some sort of netlify configuration.

Is that possible?

I’m aware of the netlify.toml file to configure redirection, but using that will cause the same redirection to happen in both websites.

Yes, you can create 2 HTML files in the root of the repo. You can then write different build commands for each website. It can look like cp index1.html public/index.html && CI= num run build. Then you can set a different build comma for another website by changing index1.html to index2.html. Make sure your netlify.toml file does not have a build command, for this to work.