Hi and thanks for taking a look.
I didn’t find any free RSS client (bot) for Telegram without ads. It probably can be done with email notifications forwarded to Telegram bot, however I didn’t investigate it yet.
I believe if it could be done without extra plugin, that plugin would never be created.
You can receive push notifications from Discourse Android app? I only see number of notifications when I launch app, it’s not really useful as I do not use any other Discourse site.
Plugin looks solid to me - it’s maintained for more than 5 years, by someone from core Discourse team members, have regular updates and many active installations.
EDIT
I looked into:
and it seems it could be possible without plugin - but not easier to maintain as it requires writing some code, keeping it running and dealing with sensitive data. I know that you expect someone else to handle it, I’d like to have this feature working somehow, so we have different perspectives 
There was a thread previously about RSS with notifications - seems it’s not possible (yet).