I use a Telegram bot.. I create a channel for each RSS feed (or a bunch of related feeds) and then add the bot to it and use some /commands, and the bot will send posts to it. I can invite other people to the channel too, and Telegram even lets you add a little chat to discuss each submission separately

The bot is @rss2tg_bot, if you don't want channels you can just begin a private chat with it and send a rss url. Or add it to a group and then it sends new posts to the group.