firstname_lastname.txt

Main types of country/city specific websites for search by first/last name 
Civil records
Court records
Voter recors
Ancestor databases
Business registries
License registries
Debtors registries
Real estate owners registries
General rule: country register is better than world register. The city register is better than the country register. A neighbourhood register is better than a city register.
Social media mentions universal search
social-searcher.com
Username by first/last name generation
NAMINT (https://seintpl.github.io/NAMINT/)
Username generation guide (https://github.com/soxoj/username-generation-guide)
For username search use "USERNAME OSINT" cheat sheet
First name variations
https://nameberry.com/search?q=john
Generate possible emails by first and last name
https://docs.google.com/spreadsheets/d/17URMtNmXfEZEW9oUL_taLpGaqTDcMkA79J8TRw4xnz8
For email search use "EMAIL OSINT" cheat sheet
!Using search engines don't forget to write names in the Latin alphabet and use differet first name variations!
Google queries
 intitle:first name intitle:last name
 inurl:first name inurl:last name
first name last name filetype:xls
first name last name filetype:xlsx
first name last name filetype:sql
Marple (https://github.com/soxoj/marple) - tool for automation Google inurl search by first name/last name
IP search engines queries
Search in Netlas http.title:*first name*  http.title:*last name*
Search in Netlas http.meta:*first name* http.meta:*last name*
Search in Netlas ftp.banner:*first name* ftp.banner:*last name*
domain:*first name* domain:*last name*
Similar queries can also be made in Censys, ZoomEye, Onyphe, Fofa etc