When you get an email with images from that domain, click the down arrow in the allow remote images and you will be offered a list of all domains that the images in the email come from and you can allow them or not.

A more difficult way to to go to settings, search for remote. Click on the exceptions button in the allow remote content option and manually edit the list of exceptions.

Same issue here. Email from a trusted address over past decade is suddenly going to Junk as of today. Cannot see how to whitelist the Sender, and googling the question tells me to go to Tools>Options, however Options does not show in the Tools menu.

Same issue here.

Actually no it is not!

Email from a trusted address over past decade is suddenly going to Junk as of today.

I suggest you have a look at your antivirus product. Trend in particular has some sort of junk/scam filter that messes up about every time Thunderbird updates. So once a month.

Cannot see how to whitelist the Sender, and googling the question tells me to go to Tools>Options, however Options does not show in the Tools menu.

Adding an address to the address book is a automatic whitelist from Thunderbird junk filter.

If that does not fix your issue I suggest you ask your own question as what you have is not the same issue as is the topic of this thread.