How to get and install MuseScore 3 Evolution^*)

Pre-requisites for Installation

A computer meeting the specification for running 3.6.2. (See also Musescore 3 Installation Guide)
Note: Actually for Mac it needs to be macOS 10.13 at least rather than macOS 10.10.
An OS which can extract .zip archives and .7z archives (like the latest Windows 11)
-- or --
The 7-Zip File Manager (free, open-source software available from 7-Zip).
If you're fine with using a PortableApp: 7-Zip is not needed, it comes as a self-extracting archive inside a .zip archive.
A GitHub account for downloading Musescore 3.7.0 artifacts. (A free account is sufficient).
Up to date antivirus, since this is always a sensible precaution when installing software.

Installing Musescore 3.7.0

The procedure is shown for Windows 10 and takes only a few minutes. Other O/S installations are similar, although for macOS there have been reported some mixed results, esp. for Macs using Apple silicone AKA M1/M2, so for that please check this forum post. Seems the (no) sound issue has been resolved now, the lack of notarization too has been resolved now (for all builds except those for PRs)! See also https://github.com/musescore/MuseScore/wiki/Downloading-and-running-test-builds, it describes basically the same thing, but does so also for Linux and macOS, just not specificially for MuseScore 3.7 Evolution.
Navigate to the GitHub Musescore repository Jojo-Schmitz/MuseScore (well, you're here already) and login to GitHub.
Click on Actions to list "All worksflows"
Choose a 3.x workflow (preferably the top-most one) that has a green tick showing successful completion (on all builds of that group!) and that matches your OS. There now are 'nightly builds' happening every night at 4am GMT (finished about 10-30 minutes later), easily identified by their names, "Build: Linux / Check: Iunit tests (mtests)", "Build: macOS" and "Build: Windows".
Click on the workflow title to link to the workflow details page.

Workflow Details

In the Artifacts area of the workflow details (scroll down the page to see it) click on the 64-bit package (Mu3.7_xxxxxxxxx_Win64_3.x) to download it. It uses Qt 5.15, unlike 3.x up to 3.6.2, this, among other things like many bug fixes, allows for ECMAScript 7 syntax in plugins. Alternativly there's now also a PortableApp (Mu3.7_xxxxxxxxx_Win64Portable_3.x), it is also 64-bit (and is also using Qt 5.15).

Note 1: This download requires that you are logged in to GitHub.

Note 2: For some configurations of Windows the 64-bit version can be problematic (e.g. missing plugins) or not suitable at all (e.g. in a 32-bit Windows 7). If this happens then use the 32-bit package (Mu3.7_xxxxxxxxx_Win32_3.x) instead (it uses Qt 5.9 rather than Qt 5.15, just like all 3.x up to 3.6.2 did). Alternativly there's now also a PortableApp (Mu3.7_xxxxxxxxx_Win32Portable_3.x), it is also 32-bit (and is also using Qt 5.9).

Note 3: The package names will be different for MacOS and Linux.
Download the package to the Downloads folder on your computer.
Extract the .zip file to produce a .7z file For the PortableApp extract the .zip file o produce a .exe file
Extract the .7z file to produce a folder with the same name as the .7z file For the PortableApp run the .exe file
Move this new folder to a more suitable location since the downloads folder is typically only used as a staging area.
Any folder can be used, (e.g. Documents), but not a cloud sync'd folder, (OneDrive, DropBox etc). You may be asked for confirmation.
The folder contents will look similar to this:
Open the bin folder and locate the MuseScore3.exe file. For the PortableApp open the folder you specified when running the .exe
Double-click the file to run MuseScore 3 Evolution For the PortableApp double click MuseScorePortable.exe
Optional: Rename MuseScore3.exe to distinguish it from MuseScore 3.6.2, for example to MuseScore 3 Evolution.exe, or, to prevent spaces in the name, MuseScore3Evo.exe.
You can make a shortcut on the Windows Start Menu by right-clicking the .exe file and then choosing Pin to Start