Your best bet may be to Roth convert a tIRA, paying the taxes with money from a taxable account. This has the effect of shifting some of your taxable account (equal to the taxes paid) into the Roth IRA, where it is no longer taxed. Think of it this way: withdraw from tIRA, pay taxes from the withdrawn amount, leaving your net withdrawal. Now you can take that net withdrawal, add taxable money to it to bring the total back to the original tIRA withdrawal amount, and put it into the Roth. There is now more after tax value in the Roth than you had in the tIRA.
Also be sure to take advantage of your FIRE low income to make tIRA withdrawals or Roth conversions. The more you take out at low marginal tax rates, the less you have to take in RMD's later at possibly higher marginal tax rates.