Facing same issue before. i added package.json at sub module dir as workaround.
refs Feature: support new package.json exports field · Issue #670 · facebook/metro · GitHub
diff --git a/node_modules/@sendbird/chat/groupChannel/package.json b/node_modules/@sendbird/chat/groupChannel/package.json
new file mode 100644
index 0000000..3072a6e
--- /dev/null
+++ b/node_modules/@sendbird/chat/groupChannel/package.json
@@ -0,0 +1,22 @@
+{
+ "version": "4.0.0-beta-2",
+ "description": "Sendbird SDK for JavaScript",
+ "name": "@sendbird/chat",
+ "author": "Sendbird <support@sendbird.com>",
+ "keywords": [
+ "sendbird",
+ "sendbird.com",
+ "messaging",
+ "chat",
+ "js"
+ ],
+ "license": "SEE LICENSE IN LICENSE.md",
+ "homepage": "https://sendbird.com",
+ "repository": {
+ "type": "git",
+ "url": "https://github.com/sendbird/sendbird-chat-sdk-javascript"
+ },
+ "type": "module",
+ "main": "../bundles/groupChannel.js",
+ "types": "../types/groupChannel.d.ts"
+}
diff --git a/node_modules/@sendbird/chat/message/package.json b/node_modules/@sendbird/chat/message/package.json
new file mode 100644
index 0000000..95e9a3c
--- /dev/null
+++ b/node_modules/@sendbird/chat/message/package.json
@@ -0,0 +1,22 @@
+{
+ "version": "4.0.0-beta-2",
+ "description": "Sendbird SDK for JavaScript",
+ "name": "@sendbird/chat",
+ "author": "Sendbird <support@sendbird.com>",
+ "keywords": [
+ "sendbird",
+ "sendbird.com",
+ "messaging",
+ "chat",
+ "js"
+ ],
+ "license": "SEE LICENSE IN LICENSE.md",
+ "homepage": "https://sendbird.com",
+ "repository": {
+ "type": "git",
+ "url": "https://github.com/sendbird/sendbird-chat-sdk-javascript"
+ },
+ "type": "module",
+ "main": "../bundles/message.js",
+ "types": "../types/message.d.ts"
+}
diff --git a/node_modules/@sendbird/chat/openChannel/package.json b/node_modules/@sendbird/chat/openChannel/package.json
new file mode 100644
index 0000000..3072a6e
--- /dev/null
+++ b/node_modules/@sendbird/chat/openChannel/package.json
@@ -0,0 +1,22 @@
+{
+ "version": "4.0.0-beta-2",
+ "description": "Sendbird SDK for JavaScript",
+ "name": "@sendbird/chat",
+ "author": "Sendbird <support@sendbird.com>",
+ "keywords": [
+ "sendbird",
+ "sendbird.com",
+ "messaging",
+ "chat",
+ "js"
+ ],
+ "license": "SEE LICENSE IN LICENSE.md",
+ "homepage": "https://sendbird.com",
+ "repository": {
+ "type": "git",
+ "url": "https://github.com/sendbird/sendbird-chat-sdk-javascript"
+ },
+ "type": "module",
+ "main": "../bundles/groupChannel.js",
+ "types": "../types/groupChannel.d.ts"
+}