This script can export all of your TG-channels from one folder into OPML format that can be imported into any RSS-reader. RSSHub.app is used for rss-friendly urls.

exporttgfolder.py

import sys
import xml.etree.ElementTree as ET
from telethon import TelegramClient
from telethon.tl.functions.messages import GetDialogFiltersRequest
from telethon.tl.types import InputPeerChannel, DialogFilter, DialogFilterDefault, DialogFilterChatlist

api_id = '<YOUR_APP_ID>'
api_hash = '<YOUR_APP_HASH>'

# Set up the Telethon client
client = TelegramClient('session_name', api_id, api_hash)

async def export_channels(folder_name):
    # Connect to Telegram
    await client.start()
    print("Connected to Telegram!")

    dialog_filters = await client(GetDialogFiltersRequest())
    channels = []

    # Filter channels based on the provided folder name
    for filter in dialog_filters.filters:
        if not isinstance(filter, DialogFilter) and not isinstance(filter, DialogFilterChatlist):
            # print(filter.to_dict())
            continue
        if filter.title != folder_name:
            # print(filter.title+"\n");
            continue
        for peer in filter.include_peers:
            if isinstance(peer, InputPeerChannel):
                channels.append(peer)

    # OPML XML setup
    root = ET.Element("opml", version="1.0")
    head = ET.SubElement(root, "head")
    title = ET.SubElement(head, "title")
    title.text = "Exported Telegram Channels"
    body = ET.SubElement(root, "body")

    # Fetch channel details and create OPML entries
    for channel in channels:
        channel_entity = await client.get_entity(channel)
        outline = ET.SubElement(body, "outline", {
            "text": channel_entity.title,
            "type": "rss",
            "xmlUrl": f"https://rsshub.app/telegram/channel/{channel_entity.username if channel_entity.username else channel_entity.id}"
        })

    # Save the OPML file
    tree = ET.ElementTree(root)
    tree.write("export.opml", encoding='utf-8', xml_declaration=True)
    print("OPML file has been saved as export.opml")

if __name__ == '__main__':
    folder_name = sys.argv[1]
    client.loop.run_until_complete(export_channels(folder_name))