I have family in Russia and it's a sad state of affairs. Our ability to communicate with them is slowly degrading to the point where now I am looking into self-hosted communications.
(Sadly, it's just Mikrotik gear that can't use any fancy censorship evasion protocols).
But sure, they are trying their worst to block every channel of data exchange they can.
Before you ask: yes, dialup works on modern networks if the codec is G.711 (uncompressed). Most public phone network is this way because fax is a thing, but some bulk carriers or some enterprises use compressed codecs.