You can make an adjustment for the incorrect basis shown on the tax reporting statement from the brokerage firm.
See https://www.irs.gov/instructions/i8949#en_US_2021_publink1000285717
You can use the stepped-up basis for the one-half you received from your wife as a result of her passing. Note that the proper method for valuation of the ETF is to use the high plus the low for the date of death divided by two (i.e., the average of the high and low the ETF traded at that day).
Note further that you also have to file a gift tax return (Form 709).
See https://www.irs.gov/instructions/i709#en_US_2021_publink16784xd0e314
