How to install an incompatible app on your Android TV

Hello,
I may not have been clear enough, so I’ll ask my question again:
From my television, I can access the Google Play Store app and download the apps I'm interested in directly.
However, some of them are nowhere to be found.
I can find them on my MacBook by going to the Google Play Store website. However, some of them are not compatible with my television.
So, I went to my TV settings and did the following:
- Android TV settings, Security and restrictions, and on Unknown sources. There, I checked "Enabled" to allow this type of installation.
Then, I installed a file manager.
But now I'm stuck and I don’t know what to do. I tried going to an APK or AKP downloader, but once downloaded, Safari tells me that no application can open it.
What should I do to make this work? It’s important.
Thank you very much for responding clearly, I’m not very good with computers (or generally for that matter).