Hi,
there are so many cryptos and I find it hard to identify the ones where I should have a closer look.
Obviously one can find cryptos e.g. by listening to shilling on Reddit. But I'm looking for more professional sources like YouTube channels, free/ paid Telegram/Discord groups and so on. What do you use?
Everything is very easy: just visit the most popular
https://coinmarketcap.com/ site. There, you will find all the information about Bitcoin and altcoins.