I have two sour citruses... I don't know if you can call them oranges or not. One is closer to the yuzu I think.
Anyway I'm pretty sure they are shimanto-bushukan and konatsu.
Both are pretty sour, though I can just munch into a shimanto-bushukan when it's fully ripe and enjoy it. I haven't tried making marmalade from either yet, but I really like to juice them green like limes and drink with soda or
water and salt, like a power drink, they're green in summer here, so it's pretty refreshing.
I wanted to make konatsu marmalade this winter... I will put that on my to-do list for tomorrow.
I also have a kumquat tree. It's delightful. We eat the fruit off the tree and I often make marmalade from it. It's ripening up now.