I play Zero-K (a related open source game) a few times a month. I really enjoy their 'cold take' blog series discussing game mechanics and the history of TA derivatives. https://zero-k.info/mediawiki/Cold_Takes

I played a ton of ZK back in 2016-21, it's the most polished game of its kind imo. The cold takes series is excellent, rts balance is such a hard problem and it makes for interesting systems analysis.