The appended patch solves the FTBFS issue for me.
The upstream code has changed too much to apply the patch directly.
Best regards
Heinrich
diff -Nru u-boot-2025.01/debian/changelog u-boot-2025.01/debian/changelog
--- u-boot-2025.01/debian/changelog 2026-01-05 19:15:58.000000000 +0000
+++ u-boot-2025.01/debian/changelog 2026-06-02 13:33:07.000000000 +0000
@@ -1,3 +1,10 @@
+u-boot (2025.01-4) UNRELEASED; urgency=medium
+
+ * Fix FTBFS with OpenSSL 4.0 (Closes: #1138297)
+ - d/p/Fix-building-with-OpenSSL-4.0.patch
+
+ -- Heinrich Schuchardt <[email protected]> Tue, 02 Jun 2026
13:33:07 +0000
+
u-boot (2025.01-3.1) unstable; urgency=medium
* Non-maintainer upload.
diff -Nru u-boot-2025.01/debian/patches/Fix-building-with-OpenSSL-4.0.patch
u-boot-2025.01/debian/patches/Fix-building-with-OpenSSL-4.0.patch
--- u-boot-2025.01/debian/patches/Fix-building-with-OpenSSL-4.0.patch
1970-01-01 00:00:00.000000000 +0000
+++ u-boot-2025.01/debian/patches/Fix-building-with-OpenSSL-4.0.patch
2026-06-02 13:31:18.000000000 +0000
@@ -0,0 +1,32 @@
+From: Heinrich Schuchardt <[email protected]>
+Date: Tue, 2 Jun 2026 13:08:49 +0000
+Subject: [PATCH 1/1] tools: Fix building with OpenSSL 4.0
+
+The ENGINE API was permanently removed in OpenSSL 4.0.
+Use OPENSSL_ENGINE_STUBS macro to avoid a build error for rsa-sign.o.
+Suppress Wdeprecated-declarations warnings caused by the ENGINE API.
+
+(Closes: #1138297)
+
+Signed-off-by: Heinrich Schuchardt <[email protected]>
+Forwarded: no
+---
+ tools/Makefile | 3 +++
+ 1 file changed, 3 insertions(+)
+
+--- a/tools/Makefile
++++ b/tools/Makefile
+@@ -184,10 +184,12 @@
+ ifeq ($(HOSTOS),darwin)
+ HOSTCFLAGS_mxsimage.o += -Wno-deprecated-declarations
+ HOSTCFLAGS_image-sig.o += -Wno-deprecated-declarations
+-HOSTCFLAGS_rsa-sign.o += -Wno-deprecated-declarations
+ endif
+ endif
+
++# Fix building with OpenSSL 4.0
++HOSTCFLAGS_rsa-sign.o += -Wno-deprecated-declarations -DOPENSSL_ENGINE_STUBS
++
+ HOSTCFLAGS_fit_image.o += -DMKIMAGE_DTC=\"$(CONFIG_MKIMAGE_DTC_PATH)\"
+
+ HOSTLDLIBS_dumpimage := $(HOSTLDLIBS_mkimage)
diff -Nru u-boot-2025.01/debian/patches/series
u-boot-2025.01/debian/patches/series
--- u-boot-2025.01/debian/patches/series 2026-01-05 19:12:06.000000000
+0000
+++ u-boot-2025.01/debian/patches/series 2026-06-02 13:23:22.000000000
+0000
@@ -13,3 +13,5 @@
sitara/Don-t-attempt-to-build-final-firmware-images.patch
binutils-output-target.patch
+
+Fix-building-with-OpenSSL-4.0.patch
