RNE-L21 not supported
 

2019-03-15 12:47:57.795 Autodetect COM port and phone type start!
2019-03-15 12:47:58.586 Found COM port: COM8
2019-03-15 12:47:58.601 Found phone type: Huawei Android phone (HiSilicon CPU)
2019-03-15 12:47:58.802 Connecting to server...
2019-03-15 12:47:59.083 Connected!
2019-03-15 12:47:59.083 Open COM port COM8 (Android Adapter PCUI (COM8))...

Not supported/unknown chipset!

Correct, all android 8 and later with latest security patches not supported.

is it possible to download older software

No, it is not, not that it would do anything good for unsupported devices anyway.