Your rankings tanking on/around 10/19's update looks like a strong correlation. Your GSC with congruent drops in impressions and clicks doesn't immediately look like KWs you were top 3 for suddenly dropping further down the page-- else impressions would be similar but AP/CTR would just be tanking.
If you're using GA and your traffic doesn't have tons of seasonality, look at the landing page report month over month and see which pages have had the largest drop (can also do this in GSC). Then check in GSC and see what those pages' APs have done over the same period.
What types of links is GSC showing? Google says they don't count bad links, but if they make up a large proportion of your site's backlinks, SpamBrain (their spam AI-- publicly announced more frequently) may bucket your site that way.
SEMrush, ahrefs, Majestic, Moz OSE are all decent for checking who is linking (and maybe disavowing), but LinkResearchTools is probably going to focus more on identifying suspicious backlinks, if that is in fact what is impacting your site.
looking for correlation with any google change must always be the last thing to check for. if you look for correlation, you will always find some. there was an domain change and URL change with subideal old2new migration.
This would probably be captured when looking at GA in the landing page report with MoM traffic going to 0 for once high value pages. If that is the case, a 301 from old path(s) to new is the simplest solution to possibly restore most of the traffic? From what I've seen, lots of the SO scraper sites got crushed late last year, so if the top traffic driving pages historically have not had URLs changed, then maybe investigate that further. If they had their URLs changed, just redirect the old URLs and hope for the best.
@OP, if there were in fact high traffic pages that got renamed, do a CSV/Excel export in GA/GSC/sitemap/etc., and map the old URLs to their new and implement 301's and wait and see if traffic starts to return.
Your rankings tanking on/around 10/19's update looks like a strong correlation. Your GSC with congruent drops in impressions and clicks doesn't immediately look like KWs you were top 3 for suddenly dropping further down the page-- else impressions would be similar but AP/CTR would just be tanking.
If you're using GA and your traffic doesn't have tons of seasonality, look at the landing page report month over month and see which pages have had the largest drop (can also do this in GSC). Then check in GSC and see what those pages' APs have done over the same period.
What types of links is GSC showing? Google says they don't count bad links, but if they make up a large proportion of your site's backlinks, SpamBrain (their spam AI-- publicly announced more frequently) may bucket your site that way.
SEMrush, ahrefs, Majestic, Moz OSE are all decent for checking who is linking (and maybe disavowing), but LinkResearchTools is probably going to focus more on identifying suspicious backlinks, if that is in fact what is impacting your site.