What would be the best technology today to make pools safe and healthy, and NOT use chlorine?

I was reading about copper ionization [0], but there's not much online [1] to see if it's really effective or not.

[0]: https://www.intec-america.com/pools/copper-ionization/

[1]: https://pubs.acs.org/doi/epdf/10.1021/acs.est.0c06287