+BRICS internal currency : Breaking news: brics launch gold-backed unit
It’s personal but I don’t put faith in the US government and wouldn’t touch treasuries with a 10 foot pole. I would personally not keep more USD than is required for my liquidity needs.
If you do hold USD, SGOV is as secure and, at least currently, yielding somewhat more than USD cash on IBKR. As mentioned by @nabalzbhf, BOXX or another money market fund could also be an option.