Hi Stefan
I have implemented many squid proxy and 3proxy solutions for raspberry, residential and datacenter proxies.
I will implement proxy on your 4G dongles on raspberry pi and give you and easy format of IP:Port:Username:Password to simply use it as proxy everywhere.
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[ + ] Check my recent works on Proxy Systems, Squid, 3proxy and HAproxy:
https://www.freelancer.com/projects/linux/Use-Squid-Route-Proxies-Dashboard
https://www.freelancer.com/projects/bash-scripting/reseller-residential-proxies
https://www.freelancer.com/projects/nodejs/NodeJS-TCP-Server-25049714
https://www.freelancer.com/projects/html/BrightData-Script-Server-Project-for
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* We are Senior Fullstack-Developer, DevOps engineer with over 15+ years of Experience in programming such as :
# PHP #JAVA # Node.js #Perl # Python # C/C++ # BASH and so on...
Let's Discuss - READY TO START NOW!
Regards
Reza