BILZ
PIMCO Ultra Short Government Active ETF
stock NYSE ETF

If you are going to use treasuries, only use ultrashort treasury funds. Anything with a longer duration is subject to interest rate risk -- its value can fluctuate, making it unsafe to use for an emergency fund.
Good options for ultrashort treasury funds: VBIL, SGOV, USFR, TBLL, BILZ.
If you already have a brokerage account at Vanguard, Fidelity, Schwab, E\*Trade, or similar, it should be very easy to transfer your money in and buy an ultrashort treasuries fund. If you have a Roth IRA at one of those firms, you can open up a brokerage or cash management account to keep your emergency fund.
Advantages -- dividends from the fund are very likely to be exempt from state income tax, if that is a thing for you. Interest from a HYSA will not be exempt from state income tax.
A HYSA like Marcus, Ally Bank, or Wealthfront may be easier to open and fund and to take money out of than working with a brokerage and buying and selling ultrashort treasury funds, particularly if you don't already have a brokerage account. Another possible advantage is that it might be easier to use Zelle with a HYSA than it typically is with a brokerage.

If you are going to use treasuries, only use ultrashort treasury funds. Anything with a longer duration is subject to interest rate risk -- its value can fluctuate, making it unsafe to use for an emergency fund.
Good options for ultrashort treasury funds: VBIL, SGOV, USFR, TBLL, BILZ.
If you already have a brokerage account at Vanguard, Fidelity, Schwab, E\*Trade, or similar, it should be very easy to transfer your money in and buy an ultrashort treasuries fund. If you have a Roth IRA at one of those firms, you can open up a brokerage or cash management account to keep your emergency fund.
Advantages -- dividends from the fund are very likely to be exempt from state income tax, if that is a thing for you. Interest from a HYSA will not be exempt from state income tax.
A HYSA like Marcus, Ally Bank, or Wealthfront may be easier to open and fund and to take money out of than working with a brokerage and buying and selling ultrashort treasury funds, particularly if you don't already have a brokerage account. Another possible advantage is that it might be easier to use Zelle with a HYSA than it typically is with a brokerage.