Thank you all for the responses.
I was able to find an hour to finally focus on this - I have a toddler and an 9 month old at home.
Here is the outcome:
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Josh is correct, there is no need to disable SSL - Firefox let me continue with the expired cert
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my “what’s the easiest way to use let’s encrypt” question was answered for me when I upgraded MIAB - that functionality is built in!
I was able to get new certs for my three domains without any issue!
Thanks again!