External Port tester

https://canyouseeme.org/

Browser/Ad tracking

https://coveryourtracks.eff.org

Bufferbloat rating

https://www.waveform.com/tools/bufferbloat

Connection benchmark

https://speedtest.net
https://www.fast.com

DNS generic test

https://www.dnsleaktest.com
https://www.perfect-privacy.com/en/tests/dns-leaktest
https://one.one.one.one/help

https://dnsspeedtest.online/

DNSSEC test

https://dnssec.vs.uni-due.de/
https://0skar.cz/dns/en/
https://rootcanary.org/test.html

Adblock test

https://d3ward.github.io/toolz/adblock
https://adblock-tester.com
https://test.adminforge.de/adblock.html
https://blockads.fivefilters.org

Multitest sites

https://ping.eu
https://www.yougetsignal.com