I have around 2k USD of btc and I wanted to swap it for something but I can't decide whether to buy eth or Solana both seem extremely promising in the far future.
Do you want to sell Bitcoin and buy Ethereum or Solana? If you hold Bitcoin for a long time then you can earn a lot of profit from investing in Bitcoin. Both Solana and Ethereum are very good to invest. You can invest in both Ethereum and Solana. Of your $2000 dollars, put 50% in Bitcoin and 30% in Ethereum and 20% in Solana. Many other people have suggested here, you can invest according to the advice that seems good to you.
In terms of ROI ETH and Solana have more upside potential than bitcoin and as both of those altcoins are major players in the market so they are safer than most of the altcoins on the market. But bitcoin is the OG of the industry, and all the major players are using it, which gives it more legitimacy and SEC also declared bitcoin a commodity, so it is safer than any other altcoin on the market. If you have a small fund then go with the alts that will give you more profit but if you have millions of dollars bitcoin is the safest option for you.