Nowadays, component supply chain issue is quite common and designers need to do component cross referencing from different suppliers. Here are a list of cross reference component search websites from manufacture and others.
If you guys have more useful links, please leave it in comment session.
Other Sites
https://octopart.com/?gclid=EAIaIQobChMI6OKQw5y49wIVcZNmAh1mqwCpEAAYASAAEgLvivD_BwE
https://partcross.com/semiconductor-manufacturers/Atmel/
http://ebook.pldworld.com/_Semiconductors/Atmel/Databook%20CDROM/Atmel/xref2.htm
https://gct.co/connector-cross-reference
http://www.cross-parts.com/news/shortcut/shortcut-data/L23.html
https://clockworks.microchip.com/microchip/crossref
http://www.cross-parts.com/news/M_search.php?nWord=NEC
https://www.we-online.com/web/en/electronic_components/produkte_pb/toolbox_pbs/Cross_Reference_1.php