I just dug through a lot of the issues and PRs in Goja, and eventually found that the grafana/k6 team recently forked Goja as Sobek [1], because the Goja dev has not been able to dedicate sufficient time to their PRs - namely ES Modules support [2], which was one of the only modern (ES6+) JS features outstanding [3]
So, Sobek seems to be the way forward...
[1] https://github.com/grafana/sobek/