You’re welcome.
It seems the culprit is the new RSA certificate issued for api.senso.community yesterday, Tue, 12 Mar 2024 22:40:14 UTC.
I just compiled the nettigo firmware with this little change and HTTPS is working again:
diff --git a/platformio.ini b/platformio.ini
index fceb2c6..b4cb4a4 100644
--- a/platformio.ini
+++ b/platformio.ini
@@ -17,7 +17,6 @@ extra_configs =
build_flags =
-D PIO_FRAMEWORK_ARDUINO_LWIP2_LOW_MEMORY
- -D BEARSSL_SSL_BASIC
-D VTABLES_IN_DRAM
-D HTTPCLIENT_1_1_COMPATIBLE=0
-D DEBUG_ESP_OOM
Removing the BEARSSL_SSL_BASIC definition makes the firmware aware of all available ciphers and the sensor now uses the EC certificate from Sun, 28 Jan 2024 22:40:10 UTC.