Yeah, it would be nice to be able to replicate a warmer and sunnier climate indoors during the winter.

Another thing you can try is to use red to near infrared light which has been shown to affect the mitochondrial electron transport chain. I read "Brain Photobiomodulation Therapy: A Narrative Review" a couple of days ago which is pretty interesting.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6041198/