In my opinion, altcoins that are suitable for long-term hodl are binance coin, ethereum and chainlink maybe this is an option for your long-term altcoin in 2021
Chainlink is very good for long-term investment because the movement is relatively slow and rarely goes down from the initial price to enter the market, which indicates that Chainlink token is quite tough. other than that, actually the top-rated altcoins are still a promising investment.