Certifications aren't the be-all and end-all of the training landscape, but if it's free, the price is right. Maybe. Here's a roster of those free certs that appear valuable to me, depending on your area of interest.
CISCO SYTEMS, INC
The site skillsforall.com is one area where Cisco lists most of their no-charge classes, courses and certifications. Overall Cisco may have close to 500 online classes or courses, but this is a convenient page for programs that don't require a third party proctor (like CCNA, etc.).
JUNIPER
At juniper.net (then "training", then "free training"), one sees not free certs but free training modules for eventually taking the test for paid certs. However, if one finishes a free module with a score of seventy percent or greater, one is awarded a 75% discount on taking the actual test. At current price schedules that's only $50, so almost free. Perhaps charging just a bit holds down the crowds and prevents slow website performance, such as the next organization typically faces...
ORACLE
At academy.oracle.com one can establish not a "member" account (unless you're an institution) but a "student" or student hub account for free. Depending upon the product family there may be dozens or more free courses of instruction. Beware of attempts to get access to a test or even the site on nights or weekends. Early in the morning would be best, since "free" is so popular.
OPSWAT
This is a provider of cybersecurity protection products that claims as clients 5 of the 10 largest US banks and 98% of all commercial and research nuclear power plants in the US. They have three levels of certification. There are the free one or two certs, then a $50 level, then a $1000 level. The two lower levels are best practices exercises of general applicability. The high priced level is for their specific products which are within the MetaDefender suite.
GOOGLE
Classes or instruction videos on these many certs can be seen on YouTube but rather than search there, it might be more profitable to use a list at reliablesoft.net. Search on "Best Google Certification Courses in 2024 (Free and Paid)". Although there's an emphasis on digital marketing (obviously for this company), many courses are available for general use of Google products and for general cyber security relevance.
AMAZON WEB SERVICES
A search (from anywhere) on the article "Make the most of AWS Training and Certification free offerings" should lead you to an Amazon page with links for many hundreds of tests and courses. Within the Amazon site also try searching for "AWS Training and Certification". AI, cloud, security and data analytics are well represented.
AZURE
Other than trying the Microsoft site or YouTube or a low-cost provider like Udemy, one can get search hits on pages like Class Central, listing over 1000 courses for capabilities and tools of this AWS competitor. And don't forget related issues such as Windows Server courses if you're on that side of the business.
Try pasting this link: https://www.classcentral.com/subject/microsoft-azure?free=true