Telegram Channels

What are the ways I can search for Telegram channels and accounts in a specific niche?
Is there a free method available?
If not, what would be a cost-effective approach to accomplish this task?
How can I obtain this information?
Please reply , get me out of this headache.

You can’t scrape Telegram channels.
Scraping groups is very easy. But there are many different websites where groups are listed. You should do a bit of surfing on Google.

You can use Telemetr, Tgstat as free version and search by keywords and "similar channels".

There are multiple websites which shows telegram groups according to search, just like discord servers. With few searches you'll be able to find it.

I have never understood why the embedded search on Telegram is so limited.

If you want to find other channels in a niche you can google for "telegram directory" and search on the sites you get there (tgdr, tgstat, etc.). Even those that offer paid services will give you a certain number of free searches (you can always bypass this using a proxy).

Once you have joined some of those groups, tho depending on the niche, I'm only certain about this on adult categories, chances are they will be running some link exchange program, which might get you into similar groups.