Hi Mark:
I'm at the same rock/hardplace as you with respect to the T41. My biggest complaint with the Arduino IDE 2.3.0 is the lack of a symbolic debugger. That said, I not going to change horses in the middle of the stream (river?). I want to keep the IDE as I know many inexperienced programmers who are comfortable with it. Also, the 2.? version of the IDE is a real step forward for that environment. Rehosting KD8CEC's software on the Teensy 4.1 should not be too bad because the resource depth is very good. While we're using a 5" RA8875 display, I'm sure a smaller, generic, TFT display will likely work well and be less expensive.
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Jack, W8TEE