1.3 - 1.6g/kg bodyweight, or 0.6 - 0.7g/lb bodyweight. That's the range to make sure you are maxing out your muscle synthesis. You can eat more, but most likely it will just end up being calorie surplus. You can probably get by with less than 1.3g/kg, but as you go further below that you are increasing the chances that you lose muscle along with fat.
All the studies are based on total body weight rather than lean mass, but for example I'm still really fat at 265lbs so I use 200lbs for my protein intake estimate. That's about 91kg, so my average daily protein intake is between 120 - 145g. I can get there with a couple hard boiled eggs or a protein bar for breakfast (15 - 20g), two cans of tuna for lunch (50 - 55g) and a chicken breast for dinner (50 - 60g). Plus veggies, which do have a few grams of protein as well (maybe another 5 - 10 total, though these aren't "complete" proteins). On days I don't get there with food, I supplement with a scoop of protein powder. Over the past year I've added a ton of strength at this level.
The caveat here you have to lift hard. Meaning select weights and rep schemes that get within a couple reps of failure for every set on every exercise. For my goals of max strength, I target of 1 - 5 reps per set on compound movements. If you're eating enough protein and just going through the motions with lifting - you're not having to really focus to get through the last couple reps, especially on the last set or two - you probably aren't lifting hard enough. You DON'T have to go to failure, ever. But you DO have to strain enough to force your body to change. The only difference between training for strength and training for growth/toning is for the latter you select lighter weights and higher reps. But you still need to get within a few reps of failure to generate enough stress to get the muscles to respond.