💚 Specify compatible Teensy @4.12 (#22448)

ini/teensy.ini

 #################################
 
 #
+# Teensy++ 2.0
+#
+[env:teensy20]
+platform   = teensy
+extends    = common_avr8
+board      = teensy2pp
+lib_ignore = ${env:common_avr8.lib_ignore}, NativeEthernet
+
+#
 # Teensy 3.1 / 3.2 (ARM Cortex-M4)
 #
 [env:teensy31]
-platform      = teensy
+platform      = teensy@~4.12.0
 board         = teensy31
 src_filter    = ${common.default_src_filter} +<src/HAL/TEENSY31_32>
 lib_ignore    = NativeEthernet
 # Teensy 3.5 / 3.6 (ARM Cortex-M4)
 #
 [env:teensy35]
-platform      = teensy
+platform      = teensy@~4.12.0
 board         = teensy35
 src_filter    = ${common.default_src_filter} +<src/HAL/TEENSY35_36>
 lib_ignore    = NativeEthernet
 
 [env:teensy36]
-platform      = teensy
+platform      = teensy@~4.12.0
 board         = teensy36
 src_filter    = ${common.default_src_filter} +<src/HAL/TEENSY35_36>
 lib_ignore    = NativeEthernet
 # Teensy 4.0 / 4.1 (ARM Cortex-M7)
 #
 [env:teensy41]
-platform      = teensy
+platform      = teensy@~4.12.0
 board         = teensy41
 src_filter    = ${common.default_src_filter} +<src/HAL/TEENSY40_41>