HSA Prior Year Contribution

I was covered by an HDHP through the ACA for all of 2021 (individual coverage).  Spouse is already is on Medicare.  Can I make a prior year contribution by April 15th  (for 2021) with the following issues?  I do NOT have an HDHP for 2022 and I will turn 65 in Nov of 2022.  I do not intend to make any contributions in 2022.

 

I did not know if the "Last Month Rule" would apply in my circumstances.

 

Also, when I do the interview in TT, it give me the max contribution for spouse (none), but it does not give me the same information.  The interview asks if I inherited the HSA, did I make a contribution, overfund in 2020, etc.  How do I get the interview to calculate the max for me? I've tried indicating no contribution and the interview just ends.   Thanks