The app store is not the only source. For every platform, the setup page lists all the routes that work: the store, TestFlight, an installer from the developer's site, or the application file. There is no need to change your account's country; there is an option for any region.
HAPP has two App Store publications: the main build in the global catalogue and the Happ Plus build in the Russian one. If the app is not in your store, open the second link from the setup page, which is usually enough.
When the App Store is no help at all, there is TestFlight: Apple's own app for test builds, with invitations to the global and Russian versions of HAPP on the same page. Install TestFlight from the store, open the invitation and confirm the install. Karing has both an App Store listing and TestFlight.
If a TestFlight link does not start an install, go back to the list of sources and try another route or another app: Clash Mi and V2RayTun install from the developers' sites and do not use the store at all.
On a Mac the store is easier to sidestep: HAPP has a DMG image you download from the site. Open it and drag the app into Applications. On first launch, macOS asks you to confirm a network extension; say yes.
If Google Play is unavailable, download the HAPP APK from the link on the setup page and open it on the device. Android asks once for permission to install apps from that source; grant it, and you can switch it back off afterwards. Karing and FlClashX are also distributed as files from their own pages.
No store is needed here at all: HAPP installs with an ordinary installer. Windows shows a SmartScreen warning; press "More info", then "Run anyway". On the first connection the system asks permission for network changes.
On Android TV without Google Play, install the Downloader app from the store, enter the address of the APK file in it and confirm the install. The TV asks you to allow installs from unknown sources for Downloader.
On Apple TV the app installs under the same Apple ID as your iPhone. If HAPP is already on the phone, it appears on the TV under Purchased, so there is no need to search the catalogue.