One drop per link the night before a ride. However I do it just a little different:
2: Align master link as a marker where to start and finish
3: One drop on each roller of the upper chain strand
4: Do something else for a minute before turning the crank (looking for clean riding gear or water bottles or whatever)
5: Repeat 3 and 4 until the master link comes up again
6: Next morning / just before the ride: wipe chain (and I recently started wiping the derailleur pulleys as well as they tend to collect grime at an annoying rate)
I used Oil of Rohloff for years and then switched to Danico Biotech (no, not the stuff that everyone wants in their arm right now) Chain Lube since it seems to be certified to rather high sustainability standards as far as I can tell. It is rated as being not hazardous to water by the German government. It's not the cleanest and not the longest lasting in terms of lubrication, but it gives me some peace of mind when the rain rinses my chain or I fall into a river.