It is worth noting that there are unique considerations regarding downloading a library from GitHub vs. installing via Library Manager. Library Manager only offers the release versions of the library. You can also obtain those from GitHub, but by default the ZIP file you download from GitHub will be the revision of the library from the tip of the default branch of the Git repository. This would generally be the development version of the library, which includes all the changes the developers made to the library since the time of the last release.
So if you wish to do beta testing, or if you require capabilities or fixes that have not yet been released, then installing the library via Library Manager will not be suitable and downloading the ZIP file from GitHub is the way to go. If your intent is to test the library and provide @ovexro with feedback, then you made the correct decision by getting the development version of the library from GitHub (since feedback on the current revision of the library is more useful than feedback on a release version which may be missing significant development work).
Conversely, for someone whose goal is only to obtain a stable library to use in their projects, they should be careful about obtaining the library from GitHub. The development/beta version of a library you will get by default may contain work that is either incomplete, or hasn't passed through the validation the maintainer would perform prior to feeling it was ready for release to production usage.
Library Manager searches against the content of the metadata that is defined by the library developers. It is even smart enough to be fuzzy in regards to the replacement characters that may be present in the header filename, but not in the metadata. For example, if you use the search query Adafruit_GFX, you will find the "Adafruit GFX Library" in the search results, even though that library's metadata does not contain the text Adafruit_GFX:
However, the search feature isn't magical. If the metadata of a library doesn't happen to contain the query in any form, then it isn't going to appear in the search results. In this case, the problem may be either that your query is not well formulated, or that the library metadata is incomplete or lacking in the detail that would provide sufficient keyword matches. If the latter, you can submit a report to the library maintainer, or a proposal for improving the metadata. Something that can be very helpful for searchability is for the library developer to add the optional includes property to the metadata. This will ensure a search for the filename of the library's primary header file will get a match in the case where the header file doesn't match against the library name.
The Library Manager search does have an advanced capability (as described here). However, it is for being more targeted in the case of queries that produce a large number of result. So it won't be helpful in the case where the target library is not present in the results for your query.