The RMDs that you received after your last qualifying event and before 2024 are intervening distributions that disqualify you from using NUA treatment with respect to this plan. Assuming that you no longer work for the employer that provides this plan, the next qualifying event would be your death after which your beneficiaries might be able to do a distribution of NUA. (Since you are receiving RMDs from this 401(k), I assume that you no longer work for this employer.)
