I just tried to setup linphone in Buster by installing flatpak and the latest version of linphone 4.1.1. Installation went smooth and it starts without any configuration (alltogether roughly ½ GB of disk space).
However trying to configure my SIP-account results in the same (or very similar) crash and segfault when password is entered: tux kernel: [ 4866.131680] linphone[6107]: segfault at 0 ip 0000003153a8f37a sp 00007ffe572604c8 error 4 in libc-2.24.so[3153a00000+194000] Mar 3 18:17:33 tux kernel: [ 4866.131690] Code: 89 e6 5b 4c 89 ef 5d 41 5c 41 5d e9 e0 49 ff ff 89 f8 31 d2 66 0f ef ff 09 f0 25 ff 0f 00 00 3d c0 0f 00 00 0f 8f 78 02 00 00 <f3> 0f 6f 0f f3 0f 6f 06 66 0f 74 c1 66 0f da c1 66 0f ef c9 66 0f So my conclusion is that this problem is more general and probably related to some function/configuration in the Debian system? Desktop environment is XFCE4. Remark: my SIP-account (Telekom) requires for registration 2 authentication cycles to register and thus to supply the password twice.