I have not seen the farmworker provisions in the reconciliation bill but I understand they are similar to the farmworker provision in the Agricultural Workers Adjustment Act of 2019 (also here) and also in Biden’s U.S. Citizenship Act of 2021. The 2019 was passed by the House with 35 Republicans voting for it. (The bill had 24 Dem and 20 Rep sponsors.) Bills to normalize the legal status of farmworkers have been proposed since at least the 2000s.
One approach to farm labor is to create a large, long term guest worker category. California farmers have opposed that option.
The U.S. Citizenship Act provisions for farmworkers in summarized here:
The farmworker provision of the bill is the largest worker legalization program and is outlined under Title I Sec. 1105 of the bill: The Agricultural Workers Adjustment Act. The act, which echoes portions of the bipartisan Farm Workforce Modernization Act that passed the House in 2019, would allow agricultural workers who have performed agricultural labor or services for at least 2,300 work hours (or 400 work days) in the five-year period before filing to get a green card. The act would also provide that the spouse and children of an eligible noncitizen agricultural worker may also adjust to permanent residence status, provided they also meet eligibility criteria. In addition, while another provision of the bill reduces the residence requirement for naturalization from five years to three years for legal permanent residents who, for at least three years before becoming a permanent resident, were both lawfully present and eligible for employment authorization, this would likely not apply to undocumented agricultural workers. However, they would be eligible to apply for citizenship after the normal five-year period if they pass additional background checks and demonstrate knowledge of English and U.S. civics.