Yes, but these extensions work by intercepting the search results to your default search engine e.g. google and then redirectin that to kagi.com.

For example you type in "hacker news" it will first redirect to https://google.com/search?q=hacker%20news the Kagi extension will intercept this and redirect you th https://kagi.com/search?q=hacker%20news but this is often a hit and miss and the Kagi extensions had/has many problems. Which all could be easier if one could just select Kagi as a search engine natively in Safari.