Is the topic of financial/trading tools just completely off-limits here, even if it’s AGPL and self-hosted?

Not necessarily. The platform (lemmy, not just c/selfhosted) is full of anti-corporate leftists and anarchists. You’re more likely to find people who want to burn the stock market to the ground than to participate in it, esp highly speculative algo trading.

I’ve seen plenty of people ask about self-hosted personal finance or portfolio tracking, so there are people for whom your project might be relevant. Just seems more like a r/wallstreetbets kind of thing than a lemmy kind of thing.

If you’re in the Western hemisphere, NOAA has every-5-minute satellite images, using the form

https://cdn.star.nesdis.noaa.gov/GOES16/ABI/SECTOR/se/GEOCOLOR/600x600.jpg

https://www.star.nesdis.noaa.gov/GOES/index.php will help you pick which SECTOR is most relevant.

Could they be astroturfing, looking for a specific solution to fill search engines with their own product placement, then deleting because most of the comments are other FOSS solutions?