Based on the current very top picture there are three main indicators.
#1 - These are directly under and perpendicular to the loaded joists.
#2 - As mentioned in the comments the left part of the wall is under the footings for the truss.
#3 - This is actually the most damning evidence of this being load bearing... The right side of the picture. Two clues ...
Option 2 is the best of your suggestions. It's cheap and quick, but will be stable. Use any available tool (or trial and error) to measure the angle, and use lumber of adequate size to avoid crushing it behind the bolts. Also, use longer bolts as needed to get enough penetration into the post.
An option that you didn't mention is to simply extend the braces ...
That's not a structural component, at least not under normal building standards. But just to be sure, check underneath in the basement or crawlspace. Is there a support below it? If so, then it's carrying some load. If not, you're good to remove it.
Check in the attic above it. Is there anything being supported? Chance are good that the answer is no.
You don’t give a lot of info, but I’ll make some assumptions and you tell me where I’m wrong.
You live in an area that does not get much snow, based on the size and spacing of your roof joists.
Likewise, you live in an area that is not a high wind area.
You say “joists run this way”, which I assume you mean roof joists and ceiling joists.
The end wall shown ...