I did not know about autolinks - thanks for the link!
It is interesting how different parsers handle this exact situation. I usually am cautious about it because I typically am not sure how it will be handled if I am not explicit with the URL and additional text.
Its really hard to tell from a technical perspective, especially without having closely monitored all of your digital activity (and those that you have been in close contact with) in the days/weeks leading up receiving the ads. Some things that Meta could have done (in varying degrees of realism) include:
Its really hard to comprehensively and conclusively avoid all "spying" that Meta/Instagram could do to you. The best thing that you could do is something that many people aren't capable or willing to do - not install any Meta software, don't use any Meta services, block any Meta IP addresses and/or domain names, and advocate that those around you do the same.
Realistically, the best advice that youre going to get has already been said. Use the web browser instead of the app as much as possible, ideally in a different browser and/or user profile. If you must have the app installed, keep it in a separate profile and kill the app and/or profile whenever it is not in use. Review all of your security and privacy settings in all Meta apps. Review any apps/services you allowed Meta to connect to/from (and the security/privacy settings of those apps). Reduce the amount of information that you enter/share on Meta platforms. Review the other users that you are connected with on Meta's platforms.