EtherCard library without TCP
My EthernetENC library based on the original UIPEthernet library by Norbert Truchsess has settings to balance performance and memory usage. These settings are in utility/uipethernet-conf.h file or can be specified as -D parameters for compilation.
UIP_CONF_MAX_CONNECTIONS is a maximum number of connected EthernetClient connections. The default value s 4. You can set it to 0 if you don't use EthernetClient TCp connections. It will save a lot of dynamic memory.
Arduino IDE doesn't have the possibility to set defines for a sketch (For example Sloeber has it). As some workaround to set the defines for different boards for Arduino IDE, you can create a file boards.local.txt next to boards.txt file in hardware package. Set build.extra_flags for individual boards.
comment by OP:

Setting uno.build.extra_flags= -DUIP_CONF_MAX_CONNECTIONS=0 in &quot;boards.txt&quot; in the arduino IDE folder reduced program memory usage by 2442 bytes and dynamic memory usage by 290 bytes.