utilitarian wrote:
....

I attached some photos. Looking for some advice on
how to deal with this. I'm thinking of nailing in an L bracket or two
into the right angle of the post and the diagonal 2 x 4 you can see in
the pics. Also maybe nail a straight metal strap horizontally across
the post, the 2 boards, and the rafter.
....

You need a whole lot more beef than that...

As a couple of others already said you need some serious support _after_
you get the thing moved back into place.

Also, you need to

a) not let anybody or anything on it until it is repaired, and
b) get some solid bracing underneath to ensure it doesn't come down
while you're trying to work on it.

That side joist needs to have the nails cut off so it can be moved back
into alignment vertically. Then, the outer rim needs brought back in to
where it was. At that point, a plate as somebody else suggested or an
outer joist can be added and fastened thru the post or lagged w/ minimum
3/8" fasteners.

For aesthetics, rather than running another joist underneath as somebody
said for the support I'd probably get another 6x and make a ledger of it
endways about 18" long or so bolted thru the post to let the deck set
on. That should then be securely tied to the rim and thru-bolted w/
steel plate.

Agree w/ the assessment of the likely weakness of construction at the
house end as well. I'd surely assess that.

If you're not confident you can tell what's adequate and what's not, I'd
suggest getting a structural opinion.

As is, this is a serious accident about to happen...

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