Seasonal Worker Solidarity Act of 2020 This bill modifies the H-2B (temporary nonagricultural workers) visa program and expands protections for aliens who report workplace violations. Changes to the H-2B program include requiring the Department of Labor to establish a centralized national electronic platform for U.S. workers to find and apply for positions that employers are seeking to fill with H-2B workers; requiring employers to recruit U.S. workers nationwide, including by posting the openings on the platform, before applying for H-2B visas; requiring employers to guarantee at least 40 hours of paid work per week for each H-2B worker (currently employers may guarantee less paid hours in certain instances); requiring employers to pay for housing for H-2B workers and transportation to and from the work site (currently employers are allowed to deduct fees for lodgings from an H-2B worker's pay); modifying the requirements for determining the minimum wage for H-2B workers; and prioritizing H-2B visas for certain employers, such as those that pay higher wages. Furthermore, an alien who has worked a certain amount of time as an H-2B worker may obtain permanent resident status, subject to various requirements. In addition, an alien who is likely helpful in an investigation of a workplace claim (i.e., an alleged violation of law or workplace-related injury) may qualify for a U visa for victims of criminal activity. The bill also removes statutory numerical limitations on U visas. The bill also provides protections for certain aliens who file or assist in the investigation of workplace claims.