Olá, fiz umas modificações ve se esta correto.

import React from 'react';
import { View, Text, TouchableOpacity } from 'react-native';

import { NavigationContainer } from '@react-navigation/native';
import { createStackNavigator } from '@react-navigation/stack';
import { createBottomTabNavigator } from '@react-navigation/bottom-tabs';

function Home({ navigation }) {
return (
<View style={{ backgroundColor: '#ffff00', justifyContent: 'center', alignItems: 'center', flex: 1, }}>

Pagina inicial

{['Pagina SOM'].map((item) => {
return (
<TouchableOpacity
key={item}
onPress={() => {
navigation.navigate('SOM')
}}
>

{item}


)
})}

)
}

function SOM({ navigation }) {
return (
<View style={{backgroundColor: '#ffff00', justifyContent: 'center', alignItems: 'center', flex: 1, }}>

Pagina inicial

{['Pagina Discover'].map((item) => {
return (
<TouchableOpacity
key={item}
onPress={() => {
navigation.navigate('Discover')
}}
>

{item}


)
})}

)
}

function Discover({ navigation }) {
return (
<View style={{backgroundColor: '#ffff00', justifyContent: 'center', alignItems: 'center', flex: 1, }}>

Pagina inicial

{['Pagina Home'].map((item) => {
return (
<TouchableOpacity
key={item}
onPress={() => {
navigation.navigate('Home')
}}
>

{item}


)
})}

)
}

const PodcastsStack = createStackNavigator();

const Tab = createBottomTabNavigator();
function MyTabs() {
return (
<Tab.Navigator>
<Tab.Screen name="Home" component={Home} />
<Tab.Screen name="SOM" component={SOM} />
<Tab.Screen name="Discover" component={Discover} />
</Tab.Navigator>
);
}

export default function App() {
return (



);
}