According to my observations, the most popular altcoins in 2021 are Solona, ​​Matic, Dogecoin and Shiba Inu. they showed their best performance throughout 2021 and the altcoin is growing rapidly and is in demand by many people until now. and I also hope that in 2022 more altcoins will become popular and trend that many people are interested in. so that cryptocurrencies are increasingly crowded and trending in society.