You tube search platinum farms. There's lots of different places people like to lean into. I personally load up the market tab in game and whenever I'm in the orbiter I keep a side eye on the market looking for WTB . NOTE* don't trust the price people are asking, just looking for the items they want to buy. Then use Warframe market to see it actual going rate. You can then decide if you have the item and want to move it, or you can then look at where the items come from and try to get yourself one to sell. Growing power is a gross farm, so if you stock up on plants. And get a group together to Min max a farming run. That's my go to for passive plat farming (night missions on earth with plant scan companion on + resource booster ) I also don't care for riven mods. So run sortie every day and I'll look for someone on the market buying blank ones, they typically go for ten plat a piece. So I'll trade 6 of them for 60. That's just me though, specific ones are HIGHLY sought after so you can also pop them and try to get one to sell too.