Its clear cut discrimination, sure, but discrimination based on disability is only prohibited if it is against “a person with a disability who meets all of a position's legitimate job requirements and can perform the essential functions of the position with or without reasonable accommodation.” [0]
The question isn't “is this discrimination” but is the requirement to use the software in question a “legitimate job requirement” and/or an “essential function” that the worker cannot do without accommodation, and for which no reasonable accommodation is available with which the worker would be able to perform the function.
Its clear cut discrimination, sure, but discrimination based on disability is only prohibited if it is against “a person with a disability who meets all of a position's legitimate job requirements and can perform the essential functions of the position with or without reasonable accommodation.” [0]
The question isn't “is this discrimination” but is the requirement to use the software in question a “legitimate job requirement” and/or an “essential function” that the worker cannot do without accommodation, and for which no reasonable accommodation is available with which the worker would be able to perform the function.
[0] https://www.eeoc.gov/foia/eeoc-informal-discussion-letter-44