A string of high-profile initial public offerings (IPOs) have been withdrawn, postponed or put on hold in 2026 as investors demand greater valuation discipline and market volatility complicates fundraising plans, testing hopes for a sustained revival in global equity capital markets.Australia's Firmus became the latest casualty on Friday, scrapping a planned stock market listing that would have ranked as the country's second-largest IPO. The Nvidia-backed artificial intelligence data centre operator had been seeking a valuation of around $30.6 billion.According to Reuters, the company cited market volatility and prevailing conditions for its decision to abandon the planned listing. Firmus said it…