I started using a mouthguard a couple months ago - I’ve long refused to get a CPAP. The mouthguard combined with sleeping in a slightly elevated position has meant I wake up far less during the night and feel much more rested every morning.
Everyone considering a mouthguard should get/borrow the little device (it clips on to the end of a finger) that measures the oxygen level in your blood. As long as it stays over 95% the whole night, then a mouthguard is fine. If not. . . .