[jsn]

Not really. You can use whatever you like, the possibilities are endless. AFAIU, the most straightforward approach would be to use Android / IOS push notifications (which can't be easily blocked) to regularly push a constantly changing (to avoid censorship) URL of your backend API servers to the mobile apps.

[maccard]

Unless those urls are unique per user, then the response to that is for the blocker (Russia in this case) to install the app and block the URLs as they change

[jsn]

They don't have to be strictly unique per user. You can send out different sets of URLs to different cohorts of users, then correlate new URL blockings with client IDs to detect rogue app installations and excommunicate them. Telegram did that when Russia tried (unsuccessfully) block it.