PulseAudio in Termux doesn't have glib feature.
This patch replaces the glib mainloop with the primary basic mainloop.
--- src/src/pavucontrol.cc	2021-04-13 18:13:27.000000000 +0000
+++ src.mod/src/pavucontrol.cc	2021-05-20 13:56:35.699908000 +0000
@@ -25,7 +25,7 @@
 #define PACKAGE_VERSION "0.1"
 
 #include <pulse/pulseaudio.h>
-#include <pulse/glib-mainloop.h>
+#include <pulse/mainloop.h>
 #include <pulse/ext-stream-restore.h>
 #include <pulse/ext-device-manager.h>
 
@@ -688,9 +688,9 @@
     if(parser.isSet(maximizeOption))
         mainWindow->showMaximized();
 
-    pa_glib_mainloop *m = pa_glib_mainloop_new(g_main_context_default());
+    pa_mainloop *m = pa_mainloop_new();
     g_assert(m);
-    api = pa_glib_mainloop_get_api(m);
+    api = pa_mainloop_get_api(m);
     g_assert(api);
 
     connect_to_pulse(mainWindow);
@@ -706,7 +706,7 @@
 
     if (context)
         pa_context_unref(context);
-    pa_glib_mainloop_free(m);
+    pa_mainloop_free(m);
 
     return 0;
 }
--- src/CMakeLists.txt	2021-04-13 18:13:27.000000000 +0000
+++ src.mod/CMakeLists.txt	2021-05-20 13:57:15.588923000 +0000
@@ -42,7 +42,6 @@
 pkg_check_modules(
     PULSE REQUIRED
     libpulse>=5.0
-    libpulse-mainloop-glib>=0.9.16
 )
 
 add_subdirectory(src)