These speculators may want to purchase an existing extension and its installed base of users, or partner with the extension developer to add third-party functionality.
Developer Armin Sebastian wrote about receiving such messages back in 2019
https://armin.dev/blog/2019/08/supporting-browser-extension-developers/
The Gen Digital Global Privacy Statement [PDF] describes various ways in which the business uses data and the conditions under which it shares data with partners.
(PDF URL)
Simeon Vincent, who until recently served as developer advocate for Chrome extensions at Google and now consults on the subject, revisited the issue in a Tuesday blog post discussing efforts to have developers integrate third-party code into their extensions
https://dotproto.com/2023/06/06/a-warning-about.html
His concern is that developers should avoid doing deals that will get them and others banned from extension-marts.