The PragProg folks have a new book that includes exercises and looks very promising as an introductory material. It's available in beta state and apparently about to be finished: https://pragprog.com/titles/nmquantum/
It took me years to notice a flaw in this approach: it's based in the premise that everyone has time for side projects.
From that point I think about it as a bias. Nowadays I try to assess if the candidates with no public activity on GH and no side projects have the passion and interest I look for, but can't take it further outside of work due to their specific circumstances.
"On Tuesday June 9th 2020 Heroku changed the certificate used for terminating TLS for built-in <appname>.herokuapp.com hostnames from a certificate issued by DigiCert to one issued by Starfield/AWS. This change was rolled back on June 10th because a small subset of Heroku customers had pinned apps to the DigiCert certificate or had apps that could not establish a chain of trust with the new certificate for other reasons.
A new DigiCert-signed certificate will replace the current one before June 22nd (when it expires)."