Not sure what your criteria for "good, safe" is but if you're interested in similar asset classes:

Government bonds in foreign currencies. Of course this exposes you to whatever that country does with their central bank and to foreign exchange rates.

Corporate bonds, obviously riskier than government bonds but at least you can get positive interest rates in your preferred currency

Preferred stock, which are similar to bonds. Before you invest in these, make sure you know how they work. They can be called back by the issuer

Other asset classes which are less safe but could help you diversify: crypto, commodities and precious metals, collector's items and art, foreign currencies. Wouldn't really recommend putting too much money in this

Invest in reducing your energy bill if you haven't done so yet. solar plus storage plus house isolation. Should also raise the value of the house. In theory.

Take the portion you want to protect with least risk, divide it into $250K chunks (the FDIC limit) and put each in a savings account with a different bank. You'll make a small interest rate and you'll have FDIC insurance covering the entire amount. That's safer than any of the Treasury securities since you will still have the backing of the US government, you can use it to rebalance your portfolio at any time, and you don't have interest rate risk. This is one area where you have an advantage over the big players like Pimco, who can't protect themselves with FDIC insurance.

If in the U.S., buy your $10k quota of Savings Bond, Series I: Pays at least the CPI-U inflation rate, liquid after one year, favorable tax treatment, highly convenient.

https://treasurydirect.gov/indiv/research/indepth/ibonds/res...

If you expect interest rates to decline, bonds still make sense as their value increases. US fiscal policy is unlikely to have negative rates in the foreseeable future.

It's only government bonds that go negative. Corporate bonds will always provide a positive yield.

Bitcoin and gold imo, in addition to a balanced portfolio of stocks, bonds and real estate.

Bitcoin.