Nepal Tourism Board, the country’s tourism promotional body, and 13 travel trekking organizations and trade unions, decided that effective from April 1, 2023 individual backpackers would not be allowed to trek in Nepal’s Himalayas without a guide. It is made mandatory for trekkers to have a trekking guide while going to trek up in the mountains. Solo travelers as well as groups are required to hire trekking guides during their trekking duration.
Source: https://kathmandupost.com/money/2023/03/14/nepal-ends-solo-trekking-era-everest-region-is-an-exception