As per SAP Blog, Jan 2020 onward download & upload process of SAP note from SNOTE transaction will stop until unless SNOTE is enabled in ABAP systems to with Digitally signed SAP Notes.
This is the secure method to download the SAP notes & all SAP note will get download only as SAR files.
Below are the SAP note which is helpful for Configuring the same.
Enable Note Assistant (SNOTE) for downloading and uploading digitally signed SAP Notes,
please implement SAP Notes 2408073, 2546220 and 2508268.
2576306 – Transport-Based Correction Instruction (TCI), it contains the SAP Notes 2408073, 2546220 and 2508268. If the SNOTE in your ABAP system is already enabled for TCI, It is recommended to implement only TCI SAP Note 2576306 instead of applying the above individual SAP Notes.
You can download the instructions from Support Portal with Subject – SAP Note Transport-Based Correction Instructions.