As reported by Peter Michael Green in Debian Bug #939399:

Hi, libgeotiff just failed to build in raspbian bullseye with the following message.

============================================
Running ../test/testlistgeo using ../bin/listgeo:
============================================
proj_create: unrecognized format / unknown name
proj_create: unrecognized format / unknown name
proj_create: unrecognized format / unknown name
proj_create: unrecognized format / unknown name
proj_create: unrecognized format / unknown name
proj_create: unrecognized format / unknown name
proj_create: unrecognized format / unknown name
proj_create: unrecognized format / unknown name
proj_create: unrecognized format / unknown name
proj_create: unrecognized format / unknown name
diff testlistgeo_out with testlistgeo_out.dist
--- testlistgeo_out    2019-09-04 06:58:26.979704475 +0000
+++ ../test/testlistgeo_out.dist    2019-09-04 06:57:50.000000000 +0000
@@ -1697,11 +1697,11 @@
     Keyed_Information:
        GTModelTypeGeoKey (Short,1): ModelTypeProjected
        GTRasterTypeGeoKey (Short,1): RasterPixelIsArea
-      ProjectedCSTypeGeoKey (Short,1): Code-3035 (ETRS89-extended / LAEA Europe)
+      ProjectedCSTypeGeoKey (Short,1): Code-3035 (ETRS89 / LAEA Europe)
        End_Of_Keys.
     End_Of_Geotiff.
-PCS = 3035 (ETRS89-extended / LAEA Europe)
+PCS = 3035 (ETRS89 / LAEA Europe)
  Projection = 19986 (Europe Equal Area 2001)
  Projection Method: CT_LambertAzimEqualArea
     ProjCenterLatGeoKey: 52.000000 ( 52d 0' 0.00"N)

PROBLEMS HAVE OCCURRED
test file testlistgeo_out saved

It also failed in the same way on the Debian reproducible builds site for bullseye armhf. The reproducible builds site has not yet tested it on other architectures in bullseye. It seems to be fine in unstable.

test/testlistgeo_out.dist may need to become a template to handle different output depending on which version of PROJ it was built with.