I usually play on normal difficulty but whenever I'm building nether tunnels I almost always switch the difficulty to peaceful ghasts can't destroy the bridge I'm building. Ever since 1.14.0 however, ghasts seem to spawn in the nether regardless of whether I've set the difficulty peaceful or not. This bug has still not been fixed and/or resolved as of v1.14.20 and affects multiple versions such as Nintendo Switch, PS4 and Mobile.