There are no I bond funds. They aren’t sold on the secondary market so you can only buy and sell them through the Feds.
TIPs can be bought in the secondary market through mutual funds and ETFs. Sadly they end up being like any other bonds when in funds and are getting beaten up this year with interest rates going up.
True, but there are bond funds designed to mimic stuff that you can't buy. The various inflation proof bond funds did great when interest rates were dropping but now that real inflation is here (and interest rates are going up) the inflation proof bond funds are dropping. There is no "safe" investment that protects from inflation and raising interest rates at the same time. Some sort of commodity play can make money but those aren't considered to be "safe". Real estate might work out okay or gold, but those all have risks too. REITs are fairly safe when the economy is good, but raising interest rates and a looming recession are bad news.
