Am I finally getting it?
Almost. I think you are mixing Total Income with AGI and MAGI and maybe a couple other things.
The standard deduction is $12k. The 10% bracket is the next $9,525. Qualified dividends and long term capital gains get taxed with total income above $50,600.
If you make a Roth conversion up to the 12% bracket you are paying some tax at 10%. That is pretty good, but it isn't zero tax.
Limit the conversion to the Standard Deduction ($12k, not a penny more) to get 0%.
You can then realize long term capital gains of up to $50,600 minus whatever other income you have (including Roth conversion.) With only a $12k Roth conversion you could realize $38,600.
This is GAINS. If your investment has doubled since you bought it, you could sell $77,200 worth... half is gain, half is basis.
These transactions will be taxed by your State, if applicable. They will also impact ACA subsidies, if applicable.