SimpleX, signal, elements, 0xChat come to mind. really depends how you were using telegram and what your privacy needs are
Discussion
Simplicity, E2EE, foss, cross platform support. Low hanging fruit for people to easily migrate to.
AFAIK simplex only works on a single device but the privacy benefits are great. Probably more tinfoil than most people need
Signal seems like a pretty good option to replace your default messenger/phone app but I don’t know how it compares to telegrams group chat features
I like Element/matrix but I’ve always had minor issues when self hosting. Mostly connection problems (probably my fault)
Haven’t tried 0xChat much so I can’t really comment
nothing compares to telegrams group chat size capabilities. Oxchat desires to be able to have 100k+ group capability, nostr:nprofile1qqs84k6jpsav0jmdeqjn2zxlpnsajaw6f8l0m2d4e9t8gjsyn53s4nspzemhxue69uhhyetvv9ujuvrcvd5xzapwvdhk6qgdwaehxw309aukzcn49ekk2qghwaehxw309aex2mrp0yh8x6tpd4ehgu3wvdhk6pw0r8j?