Note about the double capitalization: In Dutch, “IJ” is considered its own letter, making the English sound “ay.” This name is pronounced somewhat like “AYS-brawnts”.
Honestly I came to this name by accident, and I was so surprised when I saw this; two capital letters! Also the "brand" part makes it stand out noticeably.
• https://nl.wiktionary.org/wiki/IJsbrand (in Dutch)
• https://nl.forvo.com/search/IJsbrand/nl/ (in Dutch)
Converted to IPA, it should be: /'ɛi̯s.brɑnt/ [noted -ed]