I found a gem called the Euler Archive and I was looking for similar easy access to Gauss' works but I couldn't find it via google searches so I beseech thee
The published version of Gauss's collected works, which contains 12 volumes (together with two other volumes that contain treatises by later mathematicians about different aspects of Gauss's work), can be accessed freely on the digital library of Gottingen university - here is a link: https://gdz.sub.uni-goettingen.de/volumes/id/PPN235957348. This version contain all of Gauss's publications, together with a lot of unpublished manuscripts, drafts of treatises and etc.
In addition, there are published correspondences of Gauss with different mathematicians/scientists with whom he corresponded regularly. These correspondences (for examples: Gauss-Schumacher, Gauss-Bessel,...) fill many more volumes but their quality (in terms of density of mathematical ideas) is much lower than in Gauss's collected works mentioned before.
And finally, and this is something that I'm specially interested in, this is not the whole story - there are many fragments and notebooks of Gauss that have not been digitized yet - here is a link to a website that apparently gives a complete guide to Gauss's work (published as well as unpublished) - https://kalliope-verbund.info/de/findingaid_toc?fa.id=DE-611-BF-61709&fa.enum=1&lastparam=true. Note that some references that you will find in scientific/mathematical articles about Gauss cannot be located within the twelve volumes mentioned before. For example, the famous handnote in which Gauss began to study the topological object known as "braid" cannot be found in his collected works, but according to the guide in the last link, it should be found in Handbuch 7.