Define "without problems".
We currently utilise 50% -- the best, most fertile, productive 50% -- of the earth's landmass. What remains is marginal land, scrub, forests, permafrost, mountains, savannah, deserts etc, or is simply too hot or too cold for us to live comfortably. We're mistreating land with over fertilisation and suffering steady soil loss everywhere that's adopted post-war industrial agriculture. Many of those bits of rubbish land, forests and wildlife preserves we're not using are chopped up by pipelines, roads, rail affecting viability of the species broken up and interfering with natural migration and regrowth. Wildlife and wilderness has no chance.
We're clear cutting forest to make monoculture grazing land, or to plant thousands of acres of uninterrupted soya, palm oil and other major crops. As environmental awareness grows we're doing that at accelerated rate. Europe was clearcut in liveable areas in the Middle Ages, yet we've shown little to no sign of most noticing our colossal destructive impact. We just started importing big trees and colonising.
Borneo has gone from essentially untouched in the 1980s to 50% cleared now. Earth overshoot day puts us as needing 1.7 earths to sustain the current rate of regrowable use (it only considers replaceable resources, not mining and minerals). 10bn would push that up to over 2.
A sustainable population would probably be 1 or 2bn, if we want to allow a little room for the unforeseen.