The kernel firmware for your old r4 or rfi card may be found ath one of the following links:
https://www.r4wood.com/
http://www.linfoxdomain.com/nintendo/ds/
The method to use these is simple,
format your sd card,
copy the extracted files to the root of your card.
Copy any of the games , recommended that you play copy or use only legal copies if you have or the open source programs and games in your nintendo console.
Both the links have awesome collection.
Good luck.
https://www.r4wood.com/
http://www.linfoxdomain.com/nintendo/ds/
The method to use these is simple,
format your sd card,
copy the extracted files to the root of your card.
Copy any of the games , recommended that you play copy or use only legal copies if you have or the open source programs and games in your nintendo console.
Both the links have awesome collection.
Good luck.