https://www.law.cornell.edu/cfr/text/26/1.408A-6
For purposes of qualified distributions, the first contribution/conversion starts the 5 year clock. There isn't a separate clock for each conversion.
The 5-taxable-year period described in A-1 of this section begins on the first day of the individual's taxable year for which the first regular contribution is made to any Roth IRA of the individual or, if earlier, the first day of the individual's taxable year in which the first conversion contribution is made to any Roth IRA of the individual.
Thus, each Roth IRA owner has only one 5-taxable-year period described in A-1 of this section for all the Roth IRAs of which he or she is the owner.
For purposes of 72(t), 10% early withdrawal penalty, there is a separate 5 year clock for each conversion.
The 5-taxable-year period described in this A-5 for purposes of determining whether section 72(t) applies to a distribution allocable to a conversion contribution is separately determined for each conversion contribution, and need not be the same as the 5-taxable-year period used for purposes of determining whether a distribution is a qualified distribution under A-1(b) of this section.
Q-5 steers you to section 72(t). 72(t)(2)(A)(1) is relevant regarding the 10% penalty. No penalty after 59.5.
It is very confusing and I think I've got it right.
Maybe read this first:
https://www.kitces.com/blog/understanding-the-two-5-year-rules-for-roth-ira-contributions-and-conversions/