The official documentation says to use a "SN65HVD230 breakout module" and power it with 5v which is odd as that is a 3.3v chip.
A google search didn't find any 5v volt tolerant SN65HVD230 boards, so I suspect this is an error.
Check page 6 of the Ti data sheet: https://www.waveshare.com/w/upload/3/3a/SN65HVD230-CAN-Board-Datasheets.pdf It gives you two different values: Supply voltage range, VCC –0.3 V - 6 V and Supply voltage, VCC 3 - 3.6 V. A quick scan of the data sheet shows nothing operates with 5V. NXP has several transceivers that will run on both voltages, many are pin for pin compatible.
Since my last post someone has changed the 5v to 3.3v which is good, but there is still no mention of a specific breakout module and the instructions tell you to connect the D4 (CANTX0) 5v signal to the SN65HVD230 CANTX with no mention of needing to use a level shifter.
Here's a link to a video of how it should be done, and yes this contains an on screen typo showing SN65HVD3230 instead of SN65HVD230.
You can use the SN65HVD230 which is 3.3V Vcc supply rated with UNO R4 ( for Arduino Due, check CAN bus with Arduino Due - openinverter.org wiki) without a level shifter, the result will not be different for the example you refered to (below is a screenshot of UNO R4 Minima without a level shifter). That does not mean you cannot use a level shifter if you want.
Note that you are handling digital output from the Arduino board.
You can use boards TJA1050.The boards work directly powered from 5V, there is no need for a level translator. They are readily available at a low price.
The fact that it operates correctly (initially) does not mean the design is correct. Isn't this exceeding the max input voltage of the SN65HVD230 which is expecting 3.3V inputs? Presumably this will lead to premature failure of the transceiver. If I am wrong, can you clarify why this is acceptable?