No uBlock, no thanks. Any battery saving improvements given by Safari is probably negated by the volume of ads getting thrown down my throat.

uBlock is not the only ad blocker, and Safari supports many alternatives.

unfortunately ublock is the only one I trust right now. What alternative would you recommend that is fully open source and trustable?

There's a thread regarding this on github linked from gorhill's repo:

Also Adguard for Safari is GPL v3.