If you care about accuracy you should probably leave it to match content. You’ll probably have your TV calibrated to show SDR content at 100nits peak, which is a lot dimmer than most people think SDR should look.
If you want it to look bright or maybe even “pretty” you’re probably already watching SDR with a peak of like 300nits, so who really cares then anyways?
If I were to give you a tip: Give accuracy a try. Have tour TV calibrated or at least get close to more accurate setting by copying the settings of a respected calibrator and watch SDR as intended: In in dark room with a faint extra light source at most on a TV calibrated for a peak brightness of 100nits. Let your eyes and brain adjust for a few hours and chances are you’ll love it.
This is for critical viewing. Watching the news in a bright room? Who gives a fuck? Just watch it however you like. It’s like hoe critical listening to music is a completely different thing than having some music on the background while doing chores. The second doesn’t need to be accurate, but the first one really benefits from proper equipment, proper source and correct room accoustics
Are you seeing grain? Or are you seeing noise?