In order to find a solution, you have to understand the problem. It is simply a geographical block of the Play Store page. This is easily explained: the developer addresses one or more specific markets and does not want his application to be installed in other markets. There may be several reasons for this: the lack of translation in the application, focused or market-specific content, etc.
For example, we can imagine an American developer who refuses to offer his game on the French market because he wants to wait until all the content is translated, this would allow him to avoid bad marks because the game is in English.
Solution 1: VPN
There is a very simple solution: make the Play Store believe that you are in the target country. To do this, you need to change your IP address via a VPN. If you have one and are looking to configure it manually, we will explain how to do it here, and if you are looking for one you have many options at your disposal. Personally I was convinced by NordVPN but there are many others of quality, such as Express VPN to name just one.
With a few rare exceptions, free VPNs are particularly slow and often a little too intrusive. Of course, a VPN has many other uses than installing geographically inaccessible Play Store applications, it is up to you to decide if this is a necessary expense.
For practical purposes, it's very simple: connect to your VPN application and choose the country you want to connect to. Once you have done this, go to Settings > Applications (or Apps & Notifications) > Google Play Store. Then, in storage you only have to delete the data and cache it and then stop the application. Re-launch it, it will imagine itself to be in the chosen country and you can find the app. If this doesn't work at first, type from your smartphone (with the VPN turned on) the name of the app followed by Play Store, the link will then take you to the desired page and you can install it.
Solution 2: Installation by APK
If you do not want to use the Play Store, you can also install the application differently. All you have to do is find the executable file of the application to install it manually. In schematic form, it is in a way the equivalent of the setup.exe on Windows. To do this, simply go to APKMirror, search for your application and let yourself be guided to the download.