For most people I think it is best to wait until volatility comes down to more normal levels and the markets become again “investible”. TIPS or SHY makes no sense with yields near zero.
Personally I think the only strategy which make sense is to invest in equal small amounts in SPY, GLD and TLT but not by buying the ETFs but by selling ATM puts. One put will account for 100 ETFs. At the current volatilities you can buy the ETFs like this with at least 10% discount on today’s prices. If prices stabilize and the volatility will go down, then you will get the premium of 10% which is not bad. If prices will go further down you will end up with the ETFs at expiration of the puts. It is important that you sell far out options like Jan 21 or June 21. You will need to check the spreads and set limit orders in this market.
Also in no case sell too much puts. If you would buy 100 ETFs then sell only 1 put option even if you easily could sell 10 or even 100 with your margin. If you do not know anything about options, then it is probably better to stay with cash.